female reproductive system assignment

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Female Reproductive System

The female reproductive system consists of the primary as well as accessory sex organs. The primary sex organs in females are a pair of ovaries, which produce ova or egg and they also secrete female sex hormones like progesterone and estrogen. The other accessory sex organs include the uterus, fallopian tubes, cervix and vagina. The external genitalia comprises the labia minora, labia majora and clitoris. The mammary glands are not considered genital organs but are important glands in the female reproductive system.

Let’s learn more about the female reproductive system with a well-labelled diagram.

Menstrual Cycle

Reproduction control, frequently asked questions, female reproductive system anatomy.

The female reproductive system is framed to perform different functions. It creates egg cells that are essential for reproduction known as ova. The system is organized to deliver the ova to the region of fertilization. The egg fertilization takes place in the Fallopian tubes along with the sperm. The implanting in the walls of the uterus and initiating the stages of pregnancy is the next step of fertilized eggs. Apart from the above-mentioned functions, the female reproductive system is also involved in the production of female sex hormones to maintain the reproductive cycle.

The female reproductive system is composed of a pair of ovaries along with oviducts, vagina, cervix, uterus, and the external genitalia that are located in the pelvic region. These parts along with a pair of mammary glands that are integrated both functionally and structurally also support the process of ovulation, fertilization, birth and finally the child care.

Also check: Bartholin Ducts (Glands)

Ovaries act as the main female sex organs that produce the female gamete and various hormones . These organs are situated one on both the side of the lower abdomen. Each ovary measures about 2 to 4 cm in length which is then connected to the uterus and pelvic wall through ligaments. The ovary is surrounded by a thin covering of epithelium, encloses the ovarian stroma and is divided into two zones – outer cortex and the inner medulla. The cortex consists of various ovarian follicles in different stages of development. The ovarian follicle is called the basic unit of the female reproductive system. Each oviduct is divided into three anatomical regions- ampulla, isthmus, and infundibulum.

A uterus is also called the womb. It is a muscular, inverted pear-shaped organ of the female reproductive system. The walls of the uterus consist of three layers- the inner glandular layer, the middle thick layer, and the outer thin layer. These three layers are maintained by ligaments which are attached to the pelvic wall which then opens into the vagina from a narrow cervix. The cervical canal along with the vagina creates the birth canal. The vagina is a muscular tube which starts at the lower end of the uterus to the outside.

Fallopian Tubes

Fallopian tubes are a pair of muscular tubes and funnel-shaped structures, extend from the right and left of the superior corners of the uterus to the edge of the ovaries. These tubes are enclosed in small projections called fimbriae that swipe over the ovaries to pick up released ova and deliver them to the infundibulum for supplying the uterus. Each fallopian tube is covered by cilia that functions by carrying the ovum to the uterus.

Fertilization and Pregnancy

Following implantation, the placenta originates from maternal and fetal tissues, producing human chorionic gonadotropin (HCG) that helps in maintaining the level of corpus luteum in the ovary until the placenta begins synthesizing its own progesterone and estrogen hormones.

Estrogen and Progesterone

Estrogen and progesterone hormones are produced by the ovaries that foster the development of reproductive organs by maintaining the proper uterine cycle and by developing female secondary sex characteristics. During menopause, usually between age 45 and 55, the uterine cycle stops, and the ovaries are no longer produce estrogen and progesterone hormones. Infertility In general, infertility can be defined as the failure in couples of not getting pregnant, despite having carefully timed, unprotected sex for one year. It is estimated to be around 15% of all couples undergo infertility. The reasons behind this infertility in males and females are-

In Females:

Blocked oviducts.
Endometriosis.
Low sperm count.
Sperm abnormalities.

There are various birth control methods and some of them are as mentioned below.

Abstinence.
Birth control pills
Intrauterine device.
Male condom.
Contraceptive implants.
The morning after pills.

To know more about the female reproductive system and its functions, visit BYJU’S.

What are the three layers of the uterus?

The outer thin layer or the serous layer is the covering of the uterus derived from the peritoneum. Then comes the myometrium or the middle muscular layer. It is the thickest layer and is made of smooth muscle fibres. The third layer is the glandular layer called the inner mucus layer or the endometrium.

What is the cervix?

The cervix is the lower constricted part of the uterus that is divided into two portions. The upper supravaginal portion communicates with body of the uterus and the lower vaginal portion projects into the anterior wall of the vagina. The cervical canal along with the vagina creates the birth canal.

What are the functions of the ovary?

Female ovaries have two functions, endocrine and gametogenic functions. The endocrine function is the secretion of female sex hormones like the estrogen and progesterone. The gametogenic function is the production and release of the egg or ovum for reproduction.

Also check:

External Reproductive System of Women
Female External Features and Anatomy
Human External Reproductive Organs
Genital Openings in Females
Functions of Vestibule in Female Reproductive System

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Female Reproductive System Anatomy and Physiology

Step into the powerful realm of the female reproductive system anatomy and physiology. Nursing students, discover the miraculous cycles and stages that cradle and nurture life.

Fallopian tubes, mons veneris, labia minora, labia majora, skene’s glands, bartholin’s gland, perineal body, internal structures.

The ovaries are the ultimate life-maker for the females.
For its physical structure, it has an estimated length of 4 cm and width of 2 cm and is 1.5 cm thick. It appears to be shaped like an almond. It looks pitted, like a raisin, but is grayish white in color.
It is located proximal to both sides of the uterus at the lower abdomen.
For its function, the ovaries produce, mature, and discharge the egg cells or ova.
Ovarian function is for the maturation and maintenance of the secondary sex characteristics in females.
It also has three divisions: the protective layer of epithelium, the cortex, and the central medulla.
The fallopian tubes serve as the pathway of the egg cells towards the uterus.
It is a smooth, hollow tunnel that is divided into four parts: the interstitial, which is 1 cm in length; the isthmus, which is2 cm in length; the ampulla, which is 5 cm in length; and the infundibular, which is 2 cm long and shaped like a funnel.
The funnel has small hairs called the fimbria that propel the ovum into the fallopian tube.
The fallopian tube is lined with mucous membrane, and underneath is the connective tissue and the muscle layer.
The muscle layer is responsible for the peristaltic movements that propel the ovum forward.
The distal ends of the fallopian tubes are open, making a pathway for conception to occur.
The uterus is described as a hollow, muscular, pear-shaped organ.
It is located at the lower pelvis, which is posterior to the bladder and anterior to the rectum.
The uterus has an estimated length of 5 to 7 cm and width of 5 cm. it is 2.5 cm deep in its widest part.
For non-pregnant women, it is approximately 60g in weight.
Its function is to receive the ovum from the fallopian tube and provide a place for implantation and nourishment.
It also gives protection for the growing fetus.
It is divided into three: the body, the isthmus, and the cervix. f
The body forms the bulk of the uterus, being the uppermost part. This is also the part that expands to accommodate the growing fetus.
The isthmus is just a short connection between the body and the cervix. This is the portion that is cut during a cesarean section .
The cervix lies halfway above the vagina, and the other half extends into the vagina. It has an internal and external cervical os, which is the opening into the cervical canal.

External Structures

The mons veneris is a pad of fat tissues over the symphysis pubis.
It has a covering of coarse, curly hairs, the pubic hair .
It protects the pubic bone from trauma .
The labia minora is a spread of two connective tissue folds that are pinkish in color.
The internal surface is composed of mucous membrane and the external surface is skin.
It contains sebaceous glands all over the area.
Lateral to the labia minora are two folds of fat tissue covered by loose connective tissue and epithelium, the labia majora.
Its function is to protect the external genitalia and the distal urethra and vagina from trauma.
It is covered in pubic hair that serves as additional protection against harmful bacteria that may enter the structure.
It is a smooth, flattened surface inside the labia wherein the openings to the urethra and the vagina arise.
The clitoris is a small, circular organ of erectile tissue at the front of the labia minora.
The prepuce, a fold of skin, serves as its covering.
This is the center for sexual arousal and pleasure for females because it is highly sensitive to touch and temperature.
Also called as paraurethral glands, they are found lateral to the urethral meatus and have ducts that open into the urethra.
The secretions from this gland lubricate the external genitalia during coitus.
Also called bulbovaginal gland, this is another gland responsible for the lubrication of the external genitalia during coitus.
It has ducts that open into the distal vagina.
Both of these glands secretions are alkaline to help the sperm survive in the vagina.
This is a ridge of tissue which is formed by the posterior joining of the labia minora and majora.
During episiotomy , this is the tissue that is cut to enlarge the vaginal opening.
This is a muscular area that stretches easily during childbirth.
Most pregnancy exercises such as Kegel’s and squatting are done to strengthen the perineal body to allow easier expansion during childbirth and avoid tearing the tissue.
This covers the opening of the vagina.
It is tough, elastic, semicircle tissue torn during the first sexual intercourse.

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Anatomy and Physiology Nursing Test Banks . This nursing test bank includes questions about Anatomy and Physiology and its related concepts such as: structure and functions of the human body, nursing care management of patients with conditions related to the different body systems.

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StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

StatPearls [Internet].

Physiology, female reproduction.

Julie Rosner ; Tijana Samardzic ; Manbeer S. Sarao .

Affiliations

Last Update: July 7, 2022 .

Introduction

The reproductive system in females is responsible for producing gametes (called eggs or ova), certain sex hormones, and maintaining fertilized eggs as they develop into mature fetuses and become ready for delivery. A female’s reproductive years are between menarche (the first menstrual cycle) and menopause (cessation of menses for 12 consecutive months). During this period, cyclical expulsion of ova from the ovary occurs, with the potential to become fertilized by male gametes (sperm). This cyclic expulsion of eggs is a normal part of the menstrual cycle.

Development

Female gametes derive from germ cells. In utero, oogonia rapidly divide until approximately 7 million germ cells form by the 7th month of gestation. The number of germ cells then rapidly declines; most oogonia perish while the remaining cells, primary oocytes, begin the first meiotic division. These cells arrest in prophase I and remain dormant as such until menarche. [1] [2] [3] [4] A primordial follicle made up of granulosa and theca cells surrounds each oocyte. When primordial follicles mature, the granulosa cells proliferate to form concentric layers around the oocyte. The oocyte itself undergoes a drastic volume increase. With the onset of menarche, finite groups of oocytes periodically resume meiosis and continue to develop. At the time of fertilization, oocytes are arrested in metaphase II. The oocyte becomes an ovum as it expels its second polar body, and meiosis resumes when the egg undergoes activation by a sperm cell (a male gamete). [1] [2] [3] [4]

Organ Systems Involved

Female Reproductive Organs

The ovaries are female gonads, the site of gametogenesis and the secretion of sex hormones. The outer cortex of each ovary is the site of follicular development, while the inner medulla of each contains blood vessels and connective tissue. [5]

Fallopian Tubes

The vulva describes the external female genitalia: labia majora, labia minora, clitoris, vulvar vestibule, urethral meatus, and vaginal orifice. [6] The labia majora are lateral to the labia minora, fusing anteriorly to make up the mons pubis (a layer overlying the pubic symphysis). The vulvar vestibule is the area medial to the labia minora and is the location of the urethra and vaginal openings. [7] Bartholin’s glands open lateral to the vaginal opening. [6]
The vagina is a flexible, fibromuscular tubular structure extending from the vulvar vestibule to the uterine cervix. The distal vagina is the introitus. The anterior vagina abuts the posterior bladder wall, while the posterior vagina abuts the anterior rectum. [8] [9] [7] [10] [6]
The uterus consists of the corpus (body) and cervix. The superior aspect of the uterine corpus is the fundus, while the inferior portion adjacent to the cervix is called the isthmus/lower uterine segment. The uterine walls contain three distinct layers: the endometrium, myometrium, and the serosa. The endometrium lines the uterine cavity; its thickness and structure vary with hormonal stimulation. The myometrium consists of smooth muscle fibers and is the middle and thickest layer of the uterine wall. The serosa is the outermost lining of the uterus. [11]
The uterine cervix is a tubular structure contiguous with the uterine cavity and the vagina, acting as a conduit between the two. The inferior cervix opens into the upper vagina at the cervical os. The lining of the cervix that protrudes into the vagina is called the ectocervix and consists of stratified squamous epithelium. The lining of the inside of the cervical canal is the endocervix, composed of columnar epithelium. The region where the ecto- and endocervix meet, characterized by the transformation from columnar to squamous epithelium, is the transformation zone. The transformation zone is the most frequent location for cervical dysplasia and malignant transformation.
Fallopian tubes provide a passageway for oocytes to travel from the ovaries into the uterine cavity. The part of each tube closest to the ovary contains fimbria: finger-like projections that help move the expelled oocyte further into the tube—the fimbria transition into the ampulla, the part of the tube with the widest lumen. The ampulla becomes the isthmus as the lumen narrows and projects towards the uterus. The tube then passes into the uterus, where it becomes the interstitial portion. [12] This opening is where the traveling oocyte exits the tube and enters the uterine cavity.

Vulva

The vulva describes the external female genitalia: labia majora, labia minora, clitoris, vulvar vestibule, urethral meatus, and vaginal orifice. [6] The labia majora are lateral to the labia minora, fusing anteriorly to make up the mons pubis (a layer overlying the pubic symphysis). The vulvar vestibule is the area medial to the labia minora and is the location of the urethra and vaginal openings. [7] Bartholin’s glands open lateral to the vaginal opening. [6]

Menarche is a female’s first menstrual cycle, marked by her first episode of menstrual bleeding. Menarche occurs during puberty, preceded by breast growth, axillary and pubic hair growth, and a growth spurt. At the initiation of each menstrual cycle, a number of primordial follicles in the female’s ovaries continue development. One becomes the dominant follicle and continues to grow while the other follicles become atretic and cease to develop. The dominant follicle develops into a Graafian follicle, at which point meiosis I has completed, and the ovum is no longer in prophase I arrest. [1] [2] [3] [4] At ovulation, the Graafian follicle expels the ovum from its surrounding tissue, henceforth called the corpus luteum. If no fertilization takes place, the expulsion of the egg occurs from the uterus along with the secretory endometrial lining under the influence of declining levels of progesterone; this presents as menstrual bleeding. If fertilization does occur, the fertilized egg implants in the endometrial wall and the endometrial lining is maintained by progesterone secreted (initially) by the corpus luteum until the placenta takes over. [1] [2] ] [4]

The normal menstrual cycle divides into the follicular and luteal phases, with ovulation occurring between phases. The follicular phase begins with menstrual bleeding and ends right before the LH (luteinizing hormone) surge. The luteal phase begins with the LH surge and ends with the onset of menses. A typical cycle lasts approximately 28 days; the luteal phase lasts 14 days, while the follicular phase is more variable in its time course.

Low serum levels of estradiol and progesterone mark the beginning of the follicular phase. The lack of inhibitory feedback allows for an increase in pulsatile GnRH (gonadotropin-releasing hormone) levels, leading to elevations in FSH (follicular stimulating hormone) and LH. [13] [14] [15] This rise in FSH levels stimulates follicular maturation, resulting in a select number of follicles' continued growth. The growth of these follicles results in increasing FSH and estradiol levels. By the end of the follicular phase, the dominant follicle has emerged and increased to a size of approximately 20-25mm. The increase in estradiol induces thickening of the endometrium to accommodate the potential implantation of a fertilized egg.

When estradiol levels reach a critical level, the negative feedback effect of estradiol on LH becomes a positive feedback effect, resulting in a massive surge in LH concentration (and a smaller surge in FSH levels.) [13] [15] [16] Approximately 36 hours following the LH surge, the oocyte is released from the dominant follicle and travels into the uterus via the fallopian tube. [14] The corpus luteum (the remaining follicular tissue following oocyte expulsion) releases progesterone, inhibiting the release of LH and FSH and stimulating the formation of the secretory endometrium. [14] [17] In the absence of fertilization, declining LH levels contribute to a decline in progesterone and estradiol levels. [15] [16] In the presence of fertilization, the oocyte implants into the endometrium and releases chorionic gonadotropin, which maintains the corpus luteum and, thus, progesterone production. [13] [15]

Clinical Significance

The clinical relevance of female reproductive physiology comes to bear for clinical issues ranging from adolescent entry into child-bearing years, pregnancy, infertility issues, and menopause.

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Disclosure: Julie Rosner declares no relevant financial relationships with ineligible companies.

Disclosure: Tijana Samardzic declares no relevant financial relationships with ineligible companies.

Disclosure: Manbeer Sarao declares no relevant financial relationships with ineligible companies.

This book is distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits others to distribute the work, provided that the article is not altered or used commercially. You are not required to obtain permission to distribute this article, provided that you credit the author and journal.

Cite this Page Rosner J, Samardzic T, Sarao MS. Physiology, Female Reproduction. [Updated 2022 Jul 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-.

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17 Female Reproductive System

Learning objectives.

Examine the anatomy of the female reproductive system
Determine the main functions of the female reproductive system
Differentiate the medical terms of the female reproductive system and common abbreviations
Recognize the medical specialties associated with the female reproductive system
Discover common diseases, disorders, and procedures related to the female reproductive system

Female Reproductive System Word Parts

Click on prefixes, combining forms, and suffixes to reveal a list of word parts to memorize for the female reproductive system.

Introduction to the Female Reproductive System

The female reproductive system produces gametes and reproductive hormones. In addition, the female reproductive system supports the developing fetus and delivers it to the outside world. The female reproductive system is located primarily inside the pelvic cavity. The female gonads are called ovaries and the gamete they produce is called an oocyte.

Female reproductive system. Image description available.

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Practice Medical Terms Related to the Female Reproductive System

Anatomy (structures) of the female reproductive system, external female genitals.

The external female reproductive structures are referred to collectively as the vulva and they include:

The mons pubis, a pad of fat that is located at the anterior, over the pubic bone. After puberty, it becomes covered in pubic hair.
The labia majora (labia = “lips”; majora = “larger”), folds of hair-covered skin that begin just posterior to the mons pubis.
Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract.
The superior, anterior portions of the labia minora come together to encircle the clitoris (or glans clitoris), an organ that originates from the same cells as the glans penis and has abundant nerves that make it important in sexual sensation and orgasm. The hymen is a thin membrane that sometimes partially covers the entrance to the vagina .
The vaginal opening is located between the opening of the urethra and the anus. It is flanked by outlets to the Bartholin’s glands .

Internal Female Reproductive Organs

The vagina is a muscular canal (approximately 10 cm long) that is the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth. The outer walls of the anterior and posterior vagina are columns with ridges. The superior fornix meets the uterine cervix. The cervix is the opening to the uterus .

The walls of the vagina are lined with:

An outer, fibrous adventitia
A middle layer of smooth muscle
An inner mucous membrane with transverse folds called rugae .

Together, the middle and inner layers allow the expansion of the vagina to accommodate intercourse and childbirth. The thin, perforated hymen can partially surround the opening to the vaginal orifice. The Bartholin’s glands and the lesser vestibular glands (located near the clitoris) secrete mucus, which keeps the vestibular area moist .

The vagina has a normal population of microorganisms that help to protect against infection. There are both pathogenic bacteria and yeast in the vagina. In a healthy woman, the most predominant type of vaginal bacteria is from the genus Lactobacillus, which s ecretes lactic acid. The lactic acid protects the vagina by maintaining an acidic pH (below 4.5) .

Lactic acid, in combination with other vaginal secretions, makes the vagina a self-cleansing organ. However, douching can disrupt the normal balance of healthy microorganisms, and increase a woman’s risk for infections and irritation. It is recommended that women do not douche and that they allow the vagina to maintain its normal healthy population of protective microbial flora .

The ovaries are the female gonads. There are two, one at each entrance to the fallopian tube. They are each about 2 to 3 cm in length, about the size of an almond. The ovaries are located within the pelvic cavity. The ovary itself is attached to the uterus via the ovarian ligament. The ovarian stroma forms the bulk of the adult ovary. Oocytes develop within the outer layer of this stroma, each surrounded by supporting cells. This grouping of an oocyte and its supporting cells is called a follicle.

The Fallopian Tubes

The fallopian tubes, also known as uterine tubes, are the conduit of the oocyte from the ovary to the uterus. Each of the two fallopian tubes is close to, but not directly connected to, the ovary.

The isthmus is the narrow medial end of each fallopian tube that is connected to the uterus.
The wide distal infundibulum flares out with slender, finger-like projections called fimbriae .
The middle region of the tube, called the ampulla , is where fertilization often occurs.

The fallopian tubes have three layers:

An outer serosa.
A middle smooth muscle layer.
In addition to its mucus-secreting cells, the inner mucosa contains ciliated cells that beat in the direction of the uterus, producing a current that will be critical to moving the oocyte .

Did you know?

Fallopian tubes are not connected to the ovaries. Instead, fimbriae catch the oocyte like a baseball in a glove.

The Uterus and Cervix

The uterus is the muscular organ that nourishes and supports the growing embryo. Its average size is approximately 5 cm wide by 7 cm long, and it has three sections.

The portion of the uterus superior to the opening of the uterine tubes is called the fundus .
The middle section of the uterus is called the body of the uterus (or corpus).
The cervix produces mucus secretions that become thin and stringy under the influence of high systemic plasma estrogen concentrations, and these secretions can facilitate sperm movement through the reproductive tract.

The wall of the uterus is made up of three layers:

Perimetrium: the most superficial layer and serous membrane.
Myometrium: a thick layer of smooth muscle responsible for uterine contractions.
Endometrium: the innermost layer containing a connective tissue lining covered by epithelial tissue that lines the lumen. It provides the site of implantation for a fertilized egg and sheds during menstruation if no egg is fertilized.

Concept Check

Write or draw out the components of the pathway that an oocyte takes from beginning to end.
Why do you think the fallopian tubes are not connected to the ovaries ?

Physiology (Function) of the Female Reproductive System-Ovulation

Following ovulation, the Fallopian tube receives the oocyte. Oocytes lack flagella, and therefore cannot move on their own.

High concentrations of estrogen that occur around the time of ovulation induce contractions of the smooth muscle along the length of the fallopian tube.
These contractions occur every 4 to 8 seconds, causing the oocyte to flow towards the uterus, through the coordinated beating of the cilia that line the outside and lumen of the length of the fallopian tube which pulls the oocyte into the interior of the tube.
Once inside, the muscular contractions and beating cilia move the oocyte slowly toward the uterus.
When fertilization does occur, sperm typically meet the egg while it is still moving through the ampulla.

The Menstrual Cycle

The three phases of the menstrual cycle are:

The menses phase of the menstrual cycle is the phase during which reproductive hormone levels are low, the woman menstruates, and the lining is shed. The menses phase lasts between 2 to 7 days with an average of 5 days.
The proliferative phase is when menstrual flow ceases and the endometrium begins to proliferate . During this phase reproductive hormones are working in homeostasis to trigger ovulation on approximately day 14 of a typical 28-day menstrual cycle. Ovulation marks the end of the proliferative phase.
The secretory phase is when the endometrial lining prepares for the implantation of a fertilized egg. If no pregnancy occurs within approximately 10 to 12 days the endometrium will grow thinner and shed starting the first day of the next cycle.

Menopause is the cessation of the menstrual cycle that occurs as a result of the loss of ovarian follicles and the hormones that they produce, namely estrogen. The earliest changes occur during the menopausal transition, often referred to as peri menopause , when a woman’s cycle becomes irregular but does not stop entirely. As estrogen levels change, other signs and symptoms that occur are hot flashes and night sweats, trouble sleeping, vaginal dryness, mood swings, difficulty focusing, and thinning of hair on the head along with the growth of more hair on the face. Depending on the individual, these symptoms can be entirely absent, moderate, or severe.

A woman is considered to have completed menopause if she has not menstruated in a full year. After that point, she is considered postmenopausal. The average age for this change is consistent worldwide at between 50 and 52 years of age, but it can normally occur in a woman’s forties or later in her fifties. Poor health, including smoking, can lead to earlier loss of fertility and earlier menopause. After menopause, low levels of estrogen increase women’s risks of high cholesterol, cardiovascular disease, and osteoporosis .

Anatomy Labeling Activity

Practice terms related to the female reproductive system, common abbreviations for the female reproductive system.

Many terms and phrases related to the female reproductive system are abbreviated. Learn these common abbreviations by expanding the list below.

Diseases and Disorders of the Female Reproductive System

Breast cancer.

Breast cancer is the second most common cancer among women in the United States. It starts in the cells that line the ducts or the lobule of the breast. Some warning signs include a new lump in the breast or axilla , thickening or swelling, dimpling of the breast skin, redness or flaky skin, discharge, and change in breast size. Risk factors include a familial or personal history of breast cancer, obesity, hormonal treatment, and mutations in breast cancer-related genes (BRCA1 or BRCA2) (Centers for Disease Control and Prevention, n.d.-a; National Cancer Institute, 2021a).

Treatment options include chemotherapy, hormone therapy, immunotherapy, radiation, and surgical interventions such as mastectomy , and biopsy (National Cancer Institute, 2021a). To learn more about breast cancer, view the National Cancer Institute’s web page on breast cancer .

Cervical Cancer

Cervical cancer is typically slow-growing cancer and is highly curable when found and treated early. Advanced cervical cancer may cause abnormal bleeding or discharge from the vagina such as bleeding after sex. It is diagnosed during a Papanicolaou test (or Pap smear), which looks for precancerous lesions on the cervix. The Pap test can find cervical cancer early when treatment is most effective. Almost all cervical cancers are caused by human papillomavirus (HPV). The HPV test looks for HPV strains which is the virus that can cause precancerous cell changes. In the United States, a vaccine called Gardasil® 9 is available, which prevents infection with HPV and significantly reduces the risk of cervical cancer (National Cancer Institute, 2021b, 2021c). To learn more, visit the National Cancer Institute’s web page on cervical cancer .

Endometriosis

Endometriosis is an abnormal condition of the endometrium . Endometriosis occurs when this tissue grows and implants outside the uterus. The female hormone estrogen causes these implants to grow, bleed, and become inflamed. The inflammation causes scar tissue around nearby organs, which can interfere with their normal functioning and cause pain (Office on Women’s Health, 2019a).

Endometriosis generally appears in women in their 30s and 40s. Signs and symptoms may include dysmenorrhea , dyspareunia , menstrual irregularity, and infertility. Diagnosis may include laparoscopy and endometrial biopsy. There is no cure for endometriosis. Treatment may include hormonal birth control, surgical interventions such as hysterectomy and oophorectomy . The cause of endometriosis is unknown (MedlinePlus, 2021; Office on Women’s Health, 2019a). For more information, visit the Office on Women’s Health web page on endometriosis .

Polycystic Ovary Syndrome (PCOS)

Polycystic ovary syndrome (PCOS) has no known etiology, but researchers have linked it to excessive production of insulin and androgens . Excessive insulin in the body can cause insulin resistance and lead to type 2 diabetes. High levels of androgens can prevent the ovaries from releasing an egg during the menstrual cycle. The most common signs and symptoms of PCOS include oligomenorrhea , amenorrhea , polymenorrhea, one or both ovaries with multiple small painless cysts, acrochordons , acanthosis nigricans , hirsutism , thinning hair, acne, weight gain, anxiety, depression, hyperglycemia, and infertility. Treatments like medications such as birth control pills or antiandrogens can help balance the hormones in your body and relieve some of the symptoms (Office on Women’s Health, 2019b). To learn more, visit the Office on Women’s Health’s web page on endometriosis .

Sexually Transmitted Infections and Diseases (STIs and STDs)

Although the terms sexually transmitted infections (STI) and sexually transmitted diseases (STD) are often used interchangeably, they have distinct meanings. STIs refer to infections caused by a virus, bacteria, fungus, or parasite via sexual contact. STDs refer to the disease state that develops as a result of infection (U.S. Department of Health and Human Services, 2020).

Chlamydia is one of the most common sexually transmitted diseases. It is caused by the bacterium Chlamydia trachomatis, which infects the cervix and other organs of the reproductive tract in women. Chlamydia spreads through unprotected oral, anal, or vaginal sex with an infected person. Chlamydia can also spread from mother to child during childbirth. Many people with chlamydia do not have any symptoms and unknowingly pass the infection to their sexual partner(s). If symptoms develop, they may not appear for several weeks after sexual contact with an infected person. Women may have abnormal vaginal discharge, polyuria, and painful intercourse. Untreated chlamydia in women can cause pelvic inflammatory disease, which can cause permanent damage to the reproductive tract and infertility. Chlamydia is easy to treat with antibiotics and can be cured. However, until a patient finishes their treatment, they continue to have the infection and can continue to pass it to others . Patients should be re-tested three months after treatment, as re-infection is common (Centers for Disease Control and Prevention, n.d.-b).

Gonorrhea (Gonococcus)

Gonorrhea is a sexually transmitted disease caused by the bacterium Neisseria gonorrhoeae. It infects the mucous membranes of the reproductive tract, including the cervix, uterus, and fallopian tubes in women. Infections can also infect the mouth, throat, eyes, and anus. Gonorrhea is spread through unprotected oral, vaginal or anal sex with an infected person. It can also spread from mother to child during childbirth. Many people infected with gonorrhea have no symptoms and can unknowingly pass the infection on to their sexual partner(s). Signs and symptoms vary depending on which part of the body is infected. Women may have dysuria, increased vaginal discharge, or vaginal bleeding not related to their menstrual cycle. Gonorrhea infection from oral sex may lead to a sore throat, whereas infection from anal sex may cause itchiness and discharge from the anus. Untreated chlamydia can cause pelvic inflammatory disease. Gonorrhea can be treated and cured with antibiotics in combination with an intramuscular (IM) injection. However, until the patient finishes their treatment, they continue to have the infection and can pass it to others. Patients should be re-tested three months after treatment, as re-infection is common (Centers for Disease Control and Prevention, n.d.-c).

Notifiable and Reportable Diseases

In every state in the United States, chlamydia and gonorrhea are notifiable and reportable diseases. This means that when a person tests positive for either of the STIs, public health departments and the Centers for Disease Control and Prevention (CDC) are informed so that they may monitor trends, identify outbreaks, and take the necessary steps to prevent further spread of the disease (Centers for Disease Control and Prevention, n.d.-d, n.d.-e).

Human Papillomavirus (HPV)

Human papillomavirus (HPV) is another common sexually transmitted infection (STI). Both males and females can be infected with HPV. There are over 200 strains of HPV. Some strains can cause visible genital warts, while others cause genital, anal, throat, and cervical cancers . HPV spreads through sexual activity and skin-to-skin contact in the genital area with an infected person. Since some people are asymptomatic , they don’t know they have the virus and consequently pass the virus to their sexual partners. Treatments are available for genital warts but there is no cure for HPV (MedlinePlus, 2021). For more information, visit the CDC’s web page on HPV .

Herpes Simplex Virus (HSV)

Genital herpes is a sexually transmitted disease that is caused by a virus called the herpes simplex virus (HSV). There are two types of herpes simplex viruses:

Type 1- oral herpes or cold sores (HSV-1)
Type 2- genital herpes (HSV-2).

Signs and symptoms might include dysuria , enlarged glands, myalgia , and fever. Once a patient is infected with HSV, the virus remains in their body even after the symptoms are gone and can cause recurring outbreaks. When the virus becomes active again, the symptoms return but are usually less painful and heal faster (Centers for Disease Control and Prevention, n.d.-f).

Herpes is spread through direct contact with the sores or blisters of an infected person. Contact (and transfer of the virus) can occur from genitals-to-genitals, mouth-to-genitals, or mouth-to-mouth. Herpes can also be passed to the anal area. Herpes spreads easily during sexual contact while symptoms are present or just before an outbreak of symptoms. An infected person may spread herpes even when they have no symptoms; this is called asymptomatic shedding. One can spread the herpes virus to other parts of their body after touching the sores. The fingers, eyes, and other body areas can accidentally become infected in this way. Hand washing after touching sores and blisters is recommended to prevent spreading the virus (Centers for Disease Control and Prevention, n.d.-f).

There is no cure for herpes. Antiviral pills help to reduce symptoms and speed the healing of blisters or sores and are prescribed by a doctor. All sexual partner(s) should be informed. The only way to reduce the risk of transmission of herpes is to avoid direct contact with the sores and to use condoms. Condoms will reduce but not eliminate risk, as the virus can be present and shed from the skin in the genital area (Centers for Disease Control and Prevention, n.d.-f).

Common Abbreviations for Reproductive Sexually Transmitted Infections (STIs)

Medical terms in context, medical specialties and procedures related to the female reproductive system, obstetrics and gynecology.

Obstetrics and gynecology, also known as OB/GYN, is a branch of medicine focusing on the diagnosis, treatment, management, and prevention of diseases and disorders of the female reproductive system, as well as the care of women during pregnancy and childbirth. Subspecialties in women’s health include contraception, reproductive endocrinology , and infertility (National Cancer Institute, n.d.-a). To learn more, visit the American College of Surgeons’ web page on obstetrics and gynecology .

Hysterectomy

A hysterectomy is performed to stage or treat endometriosis, cancers, and precancers of the female reproductive tract, and some non-cancerous conditions that have not responded to other forms of treatment. There are three types of hysterectomy:

A total hysterectomy removes both the uterus and the cervix.
A subtotal hysterectomy removes the uterus only.
A radical hysterectomy removes the uterus, cervix, part of the vagina, and ligaments (Office on Women’s Health, 2019b).

Sometimes the ovaries and fallopian tubes are removed at the same time that a hysterectomy is done. A bilateral salpingo-oophorectomy (BSO) removes both ovaries and fallopian tubes. A unilateral salpingo-oophorectomy removes one ovary and one fallopian tube (National Cancer Institute, n.d.-b, n.d.-c). For more information, visit the Cleveland Clinic’s web page on hysterectomy .

Female Reproductive System Vocabulary

Acanthosis nigricans

A disorder that causes darkening and thickening of the armpit and other body folds.

Acrochordons

Common benign skin growths that appear as small, raised, brown or skin-colored bumps; also called skin tags.

Absence of menstruation.

Male sex hormones; for example, testosterone.

Antiandrogens

Substances that keep androgens (male sex hormones) from binding to proteins called androgen receptors. Preventing this binding blocks the effects of these hormones in the body.

Antibiotics

A drug used to treat infections caused by bacteria and other microorganisms.

Antiretrovirals

Drugs that inhibit the ability of the human immunodeficiency virus (HIV) or other types of retroviruses to multiply in the body.

Asymptomatic

Having no signs or symptoms of disease.

The underarm or armpit.

Bartholin’s glands

Glands that produce a thick mucus that maintains moisture in the vulva area; also referred to as the greater vestibular glands.

Affecting both the right and left sides of the body.

Inflammation of the cervix.

A lighted magnifying instrument used to check the cervix, vagina, and vulva for signs of disease.

A procedure in which a lighted, magnifying instrument called a colposcope is used to examine the cervix, vagina, and vulva.

Contraception

The use of drugs, devices, or surgery to prevent pregnancy.

Washing the vagina with fluid.

Dysmenorrhea

Painful menstruation.

Dyspareunia

Genital pain before, during, or after intercourse.

Painful urination.

Endocrinology

A specialty in the field of medicine that focuses on the treatment of endocrine system disorders.

A disease characterized by the presence of endometrial-like tissue found outside the uterus.

Endometritis

Inflammation of the endometrium.

Endometrium

The innermost layer of the uterus. It provides the site of implantation for a fertilized egg and sheds during menstruation if no egg is fertilized.

A procedure that uses an endoscope to examine the inside of the body.

An abnormal opening or passage between two organs or between an organ and the surface of the body.

The superior portion of the vagina.

A specialized sex cell carrying 23 chromosomes.

Gynecologist

A doctor who has special training in diagnosing and treating diseases of the female reproductive organs.

A medical-surgical specialty concerned with the physiology and disorders primarily of the female genital tract, as well as female endocrinology and reproductive physiology.

A condition in which women and children have excess coarse body hair of an adult male distribution pattern as a result of elevated androgen levels.

Homeostasis

The state of steady internal conditions maintained by living things.

Surgery to remove the uterus and, sometimes, the cervix.

Hysterosalpingogram

A radiographic image of the uterus and fallopian (uterine) tubes.

Hysteroscope

An endoscope used for examining the interior of the uterus.

Hysteroscopy

Endoscopic examination of the uterus.

A position below or lower than another part of the body proper.

Intramuscular

Within or into muscle.

Laparoscopy

A procedure that uses a laparoscope, inserted through the abdominal wall, to examine the inside of the abdomen.

White discharge from the vagina.

Acute or chronic pain in the lumbar or sacral regions.

Mammography

The use of film or a computer to create a picture of the breast.

Radiographic image of the breast.

Mammoplasty

Surgical reconstruction of the breast, including both augmentation and reduction.

Pain or discomfort in one or both breasts.

The surgical procedure to remove all or part of a breast.

A condition in which breast tissue is inflamed.

First menstruation in a pubertal female.

The cessation of the menstrual cycle; is considered complete when a woman has not menstruated in a full year.

Menorrhagia

Excessive bleeding at menstruation.

Metrorrhagia

Excessive bleeding from the uterus not related to menstruation.

Oligomenorrhea

Abnormally infrequent menstruation.

Immature egg cell.

Oophorectomy

Surgery to remove one or both ovaries.

Inflammation of the ovary.

Release of a secondary oocyte and associated granulosa cells from an ovary.

Papanicolaou smear (Pap test)

A procedure in which a small brush is used to gently remove cells from the surface of the cervix and the area around it so they can be checked under a microscope for cervical cancer or cell changes that may lead to cervical cancer.

Perimenopause

The transitional period before and after menopause wherein the menstrual cycle is irregular and hormone levels widely fluctuate.

Excessive urine production.

The protrusion of an organ or part of an organ into a natural or artificial orifice.

Proliferate

The ability to reproduce rapidly.

Time directly after childbirth.

Salpingectomy

Excision of one or both of the fallopian (uterine) tubes.

Salpingitis

Inflammation of a fallopian (uterine) tube.

Salpingo-oophorectomy

Surgical removal of the fallopian (uterine) tubes and ovaries.

Salpingostomy

Creation of an artificial opening in the fallopian (uterine) tube.

An instrument used to widen an opening of the body to make it easier to look inside.

A position above or higher than another part of the body proper.

Trachelectomy

Excision of the cervix.

Tubal ligation

Surgical closure of the fallopian (uterine) tubes for sterilization.

Pertaining to one side.

Inflammation of the urethra.

Pertaining to the vagina.

Abnormal condition of the vagina.

Excision of the vulva.

Vulvovaginitis

Inflammation of the vulva and vagina.

Test Yourself

Centers for Disease Control and Prevention. (n.d.-a). Breast cancer statistics . https://www.cdc.gov/cancer/breast/statistics/index.htm

CrashCourse. (2015, October 2015). Reproductive system, part 1 – female reproductive system: Crash course A&P #40 [Video]. YouTube. https://www.youtube.com/watch?v=RFDatCchpus

MedlinePlus. (2021). Endometriosis . U.S. National Library of Medicine. https://medlineplus.gov/endometriosis.html

National Cancer Institute. (n.d.-a). Definition of obstetrics and gynecology . National Institutes of Health, U.S. Department of Health and Human Services. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/obstetrics-and-gynecology

National Cancer Institute. (n.d.-b). Definition of bilateral salpingo-oophorectomy . National Institutes of Health, U.S. Department of Health and Human Services. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/bilateral-salpingo-oophorectomy

National Cancer Institute. (n.d.-c). Definition of unilateral salpingo-oophorectomy. National Institutes of Health, U.S. Department of Health and Human Services. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/unilateral-salpingo-oophorectomy

National Cancer Institute. (2021a). Breast cancer treatment (adult) (PDQ®)–Patient version. National Institutes of Health, U.S. Department of Health and Human Services. https://www.cancer.gov/types/breast/patient/breast-treatment-pdq

National Cancer Institute. (2021b). Cervical cancer treatment (adult) (PDQ®)–Patient version. National Institutes of Health, U.S. Department of Health and Human Services. https://www.cancer.gov/types/cervical/patient/cervical-treatment-pdq

National Cancer Institute. (2021c). Human papillomavirus (HPV) vaccines . National Institutes of Health, U.S. Department of Health and Human Services. https://www.cancer.gov/about-cancer/causes-prevention/risk/infectious-agents/hpv-vaccine-fact-sheet

Office on Women’s Health. (2019a). Endometriosis . U.S. Department of Health and Human Services. https://www.womenshealth.gov/a-z-topics/endometriosis

Office on Women’s Health. (2019b). Hysterectomy . U.S. Department of Health and Human Services. https://www.womenshealth.gov/a-z-topics/hysterectomy

Image Descriptions

Figure 17.1 image description: This figure shows the structure and the different organs in the female reproductive system. The top panel shows the lateral view with labels (clockwise from top): uterus, ovary, fornix of uterus, cervix, rectum, vagina, anus, labia majora, labium minora, clitoris, urethra, mons pubis, pubic symphysis, bladder; and the bottom panel shows the anterior view with labels (clockwise from top): ovary, ovarian ligament, broad ligament, labia minora, labia majora, vagina, cervix, uterine tube, uterus, fimbriae. [Return to Figure 17.1].

Figure 17.2 image description: This figure shows the parts of the vulva. The right panel shows the external anterior view and the left panel shows the internal anterolateral view. The major parts are labeled (from top): prepuce, glans clitoris, labia minora, corpus cavernosum, bulb of vestibule, urethral opening, labia majora, vaginal opening, the opening of right Bartholin’s gland, Bartholin’s glands, anus. [Return to Figure 17.2].

A specialized sex cell carrying 23 chromosomes (Betts et al., 2013)

The superior portion of the vagina (Betts et al., 2013)

Glands that produce a thick mucus that maintains moisture in the vulva area; also referred to as the greater vestibular glands (Betts et al., 2013)

A measure of how acidic or alkaline a substance is, as determined by the number of free hydrogen ions in the substance (Betts et al., 2013)

Washing the vagina with fluid (Betts et al., 2013)

Immature egg cell (Betts et al., 2013)

A position above or higher than another part of the body proper (Betts et al., 2013)

A position below or lower than another part of the body proper (Betts et al., 2013)

The ability to reproduce rapidly (Betts et al., 2013)

The state of steady internal conditions maintained by living things (Betts et al., 2013)

A disease characterized by a decrease in bone mass that occurs when the rate of bone resorption exceeds the rate of bone formation (Betts et al., 2013)

The underarm or armpit (National Cancer Institute, n.d.)

The surgical procedure to remove all or part of a breast (National Cancer Institute, n.d.)

The innermost layer of the uterus. It provides the site of implantation for a fertilized egg and sheds during menstruation if no egg is fertilized (Betts et al., 2013)

Painful menstruation (National Library of Medicine, 2021)

Genital pain before, during, or after intercourse (National LIbrary of Medicine, 2021)

A procedure that uses a laparoscope, inserted through the abdominal wall, to examine the inside of the abdomen (National Cancer Institute, n.d.)

Surgery to remove the uterus and, sometimes, the cervix (National Cancer Institute, n.d.)

Surgery to remove one or both ovaries (National Cancer Institute, n.d.)

Male sex hormones; for example, testosterone (Betts et al., 2013)

Abnormally infrequent menstruation (National Library of Medicine, 2021)

Absence of menstruation (National Library of Medicine, 2021)

Common benign skin growths that appear as small, raised, brown or skin-colored bumps; also called skin tags (National Cancer Institute, n.d.)

A disorder that causes darkening and thickening of the armpit and other body folds (National Library of Medicine, 2021)

A condition in which women and children have excess coarse body hair of an adult male distribution pattern as a result of elevated androgen levels (National Library of Medicine, 2021)

Substances that keep androgens (male sex hormones) from binding to proteins called androgen receptors. Preventing this binding blocks the effects of these hormones in the body (National Cancer Institute, n.d.)

pertaining to within the muscle

Having no signs or symptoms of disease (National Cancer Institute, n.d.)

Painful urination (National Library of Medicine, 2021)

Pain in a muscle or group of muscles (National Cancer Institute, n.d.)

A specialty in the field of medicine that focuses on the treatment of endocrine system disorders (Betts et al., 2013)

Affecting both the right and left sides of the body (National Cancer Institute, n.d.)

Pertaining to one side (Betts et al., 2013)

Medical Terminology for Healthcare Professions Copyright © 2020 by Andrea Nelson and Katherine Greene is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Module 11: The Reproductive System

Anatomy and physiology of the female reproductive system, learning objectives.

By the end of this section, you will be able to:

Describe the structure and function of the organs of the female reproductive system
List the steps of oogenesis
Describe the hormonal changes that occur during the ovarian and menstrual cycles
Trace the path of an oocyte from ovary to fertilization

The female reproductive system functions to produce gametes and reproductive hormones, just like the male reproductive system; however, it also has the additional task of supporting the developing fetus and delivering it to the outside world. Unlike its male counterpart, the female reproductive system is located primarily inside the pelvic cavity. Recall that the ovaries are the female gonads. The gamete they produce is called an oocyte . We’ll discuss the production of oocytes in detail shortly. First, let’s look at some of the structures of the female reproductive system.

This figure shows the structure and the different organs in the female reproductive system. The top panel shows the lateral view and the bottom panel shows the anterior view.

Figure 1. The major organs of the female reproductive system are located inside the pelvic cavity.

External Female Genitals

The external female reproductive structures are referred to collectively as the vulva . The mons pubis is a pad of fat that is located at the anterior, over the pubic bone. After puberty, it becomes covered in pubic hair. The labia majora (labia = “lips”; majora = “larger”) are folds of hair-covered skin that begin just posterior to the mons pubis. The thinner and more pigmented labia minora (labia = “lips”; minora = “smaller”) extend medial to the labia majora. Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract.

The superior, anterior portions of the labia minora come together to encircle the clitoris (or glans clitoris), an organ that originates from the same cells as the glans penis and has abundant nerves that make it important in sexual sensation and orgasm. The hymen is a thin membrane that sometimes partially covers the entrance to the vagina. An intact hymen cannot be used as an indication of “virginity”; even at birth, this is only a partial membrane, as menstrual fluid and other secretions must be able to exit the body, regardless of penile–vaginal intercourse. The vaginal opening is located between the opening of the urethra and the anus. It is flanked by outlets to the Bartholin’s glands (or greater vestibular glands).

This figure shows the parts of the vulva. The right panel shows the external anterior view and the left panel shows the internal anteriolateral view. The major parts are labeled.

Figure 2. The external female genitalia are referred to collectively as the vulva.

The vagina is a muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth. The outer walls of the anterior and posterior vagina are formed into longitudinal columns, or ridges, and the superior portion of the vagina—called the fornix—meets the protruding uterine cervix. The walls of the vagina are lined with an outer, fibrous adventitia; a middle layer of smooth muscle; and an inner mucous membrane with transverse folds called rugae . Together, the middle and inner layers allow the expansion of the vagina to accommodate intercourse and childbirth. The thin, perforated hymen can partially surround the opening to the vaginal orifice. The hymen can be ruptured with strenuous physical exercise, penile–vaginal intercourse, and childbirth. The Bartholin’s glands and the lesser vestibular glands (located near the clitoris) secrete mucus, which keeps the vestibular area moist.

The vagina is home to a normal population of microorganisms that help to protect against infection by pathogenic bacteria, yeast, or other organisms that can enter the vagina. In a healthy woman, the most predominant type of vaginal bacteria is from the genus Lactobacillus . This family of beneficial bacterial flora secretes lactic acid, and thus protects the vagina by maintaining an acidic pH (below 4.5). Potential pathogens are less likely to survive in these acidic conditions. Lactic acid, in combination with other vaginal secretions, makes the vagina a self-cleansing organ. However, douching—or washing out the vagina with fluid—can disrupt the normal balance of healthy microorganisms, and actually increase a woman’s risk for infections and irritation. Indeed, the American College of Obstetricians and Gynecologists recommend that women do not douche, and that they allow the vagina to maintain its normal healthy population of protective microbial flora.

The ovaries are the female gonads. Paired ovals, they are each about 2 to 3 cm in length, about the size of an almond. The ovaries are located within the pelvic cavity, and are supported by the mesovarium, an extension of the peritoneum that connects the ovaries to the broad ligament . Extending from the mesovarium itself is the suspensory ligament that contains the ovarian blood and lymph vessels. Finally, the ovary itself is attached to the uterus via the ovarian ligament.

The ovary comprises an outer covering of cuboidal epithelium called the ovarian surface epithelium that is superficial to a dense connective tissue covering called the tunica albuginea. Beneath the tunica albuginea is the cortex, or outer portion, of the organ. The cortex is composed of a tissue framework called the ovarian stroma that forms the bulk of the adult ovary. Oocytes develop within the outer layer of this stroma, each surrounded by supporting cells. This grouping of an oocyte and its supporting cells is called a follicle . The growth and development of ovarian follicles will be described shortly. Beneath the cortex lies the inner ovarian medulla, the site of blood vessels, lymph vessels, and the nerves of the ovary. You will learn more about the overall anatomy of the female reproductive system at the end of this section.

The Ovarian Cycle

The ovarian cycle is a set of predictable changes in a female’s oocytes and ovarian follicles. During a woman’s reproductive years, it is a roughly 28-day cycle that can be correlated with, but is not the same as, the menstrual cycle (discussed shortly). The cycle includes two interrelated processes: oogenesis (the production of female gametes) and folliculogenesis (the growth and development of ovarian follicles).

Gametogenesis in females is called oogenesis . The process begins with the ovarian stem cells, or oogonia . Oogonia are formed during fetal development, and divide via mitosis, much like spermatogonia in the testis. Unlike spermatogonia, however, oogonia form primary oocytes in the fetal ovary prior to birth. These primary oocytes are then arrested in this stage of meiosis I, only to resume it years later, beginning at puberty and continuing until the woman is near menopause (the cessation of a woman’s reproductive functions). The number of primary oocytes present in the ovaries declines from one to two million in an infant, to approximately 400,000 at puberty, to zero by the end of menopause.

The initiation of ovulation —the release of an oocyte from the ovary—marks the transition from puberty into reproductive maturity for women. From then on, throughout a woman’s reproductive years, ovulation occurs approximately once every 28 days. Just prior to ovulation, a surge of luteinizing hormone triggers the resumption of meiosis in a primary oocyte. This initiates the transition from primary to secondary oocyte. However, as you can see in Figure 3, this cell division does not result in two identical cells. Instead, the cytoplasm is divided unequally, and one daughter cell is much larger than the other. This larger cell, the secondary oocyte, eventually leaves the ovary during ovulation. The smaller cell, called the first polar body , may or may not complete meiosis and produce second polar bodies; in either case, it eventually disintegrates. Therefore, even though oogenesis produces up to four cells, only one survives.

This flowchart shows the formation of oocytes in the female. The top half of the flowchart is before birth and the bottom half is after puberty. A callout to the left also shows the eggs before and after sperm penetration.

Figure 3. Click for a larger image. The unequal cell division of oogenesis produces one to three polar bodies that later degrade, as well as a single haploid ovum, which is produced only if there is penetration of the secondary oocyte by a sperm cell.

How does the diploid secondary oocyte become an ovum —the haploid female gamete? Meiosis of a secondary oocyte is completed only if a sperm succeeds in penetrating its barriers. Meiosis II then resumes, producing one haploid ovum that, at the instant of fertilization by a (haploid) sperm, becomes the first diploid cell of the new offspring (a zygote). Thus, the ovum can be thought of as a brief, transitional, haploid stage between the diploid oocyte and diploid zygote.

The larger amount of cytoplasm contained in the female gamete is used to supply the developing zygote with nutrients during the period between fertilization and implantation into the uterus. Interestingly, sperm contribute only DNA at fertilization —not cytoplasm. Therefore, the cytoplasm and all of the cytoplasmic organelles in the developing embryo are of maternal origin. This includes mitochondria, which contain their own DNA. Scientific research in the 1980s determined that mitochondrial DNA was maternally inherited, meaning that you can trace your mitochondrial DNA directly to your mother, her mother, and so on back through your female ancestors.

Everyday Connections: Mapping Human History with Mitochondrial DNA

When we talk about human DNA, we’re usually referring to nuclear DNA; that is, the DNA coiled into chromosomal bundles in the nucleus of our cells. We inherit half of our nuclear DNA from our father, and half from our mother. However, mitochondrial DNA (mtDNA) comes only from the mitochondria in the cytoplasm of the fat ovum we inherit from our mother. She received her mtDNA from her mother, who got it from her mother, and so on. Each of our cells contains approximately 1700 mitochondria, with each mitochondrion packed with mtDNA containing approximately 37 genes.

Mutations (changes) in mtDNA occur spontaneously in a somewhat organized pattern at regular intervals in human history. By analyzing these mutational relationships, researchers have been able to determine that we can all trace our ancestry back to one woman who lived in Africa about 200,000 years ago. Scientists have given this woman the biblical name Eve, although she is not, of course, the first Homo sapiens female. More precisely, she is our most recent common ancestor through matrilineal descent.

This doesn’t mean that everyone’s mtDNA today looks exactly like that of our ancestral Eve. Because of the spontaneous mutations in mtDNA that have occurred over the centuries, researchers can map different “branches” off of the “main trunk” of our mtDNA family tree. Your mtDNA might have a pattern of mutations that aligns more closely with one branch, and your neighbor’s may align with another branch. Still, all branches eventually lead back to Eve.

But what happened to the mtDNA of all of the other Homo sapiens females who were living at the time of Eve? Researchers explain that, over the centuries, their female descendants died childless or with only male children, and thus, their maternal line—and its mtDNA—ended.

Folliculogenesis

Again, ovarian follicles are oocytes and their supporting cells. They grow and develop in a process called folliculogenesis , which typically leads to ovulation of one follicle approximately every 28 days, along with death to multiple other follicles. The death of ovarian follicles is called atresia, and can occur at any point during follicular development. Recall that, a female infant at birth will have one to two million oocytes within her ovarian follicles, and that this number declines throughout life until menopause, when no follicles remain. As you’ll see next, follicles progress from primordial, to primary, to secondary and tertiary stages prior to ovulation—with the oocyte inside the follicle remaining as a primary oocyte until right before ovulation.

Folliculogenesis begins with follicles in a resting state. These small primordial follicles are present in newborn females and are the prevailing follicle type in the adult ovary. Primordial follicles have only a single flat layer of support cells, called granulosa cells , that surround the oocyte, and they can stay in this resting state for years—some until right before menopause.

After puberty, a few primordial follicles will respond to a recruitment signal each day, and will join a pool of immature growing follicles called primary follicles . Primary follicles start with a single layer of granulosa cells, but the granulosa cells then become active and transition from a flat or squamous shape to a rounded, cuboidal shape as they increase in size and proliferate. As the granulosa cells divide, the follicles—now called secondary follicles —increase in diameter, adding a new outer layer of connective tissue, blood vessels, and theca cells —cells that work with the granulosa cells to produce estrogens.

Within the growing secondary follicle, the primary oocyte now secretes a thin acellular membrane called the zona pellucida that will play a critical role in fertilization. A thick fluid, called follicular fluid, that has formed between the granulosa cells also begins to collect into one large pool, or antrum . Follicles in which the antrum has become large and fully formed are considered tertiary follicles (or antral follicles). Several follicles reach the tertiary stage at the same time, and most of these will undergo atresia. The one that does not die will continue to grow and develop until ovulation, when it will expel its secondary oocyte surrounded by several layers of granulosa cells from the ovary. Keep in mind that most follicles don’t make it to this point. In fact, roughly 99 percent of the follicles in the ovary will undergo atresia, which can occur at any stage of folliculogenesis.

This multipart figure shows how follicles are generated. The top panel shows the six stages of folliculogenesis. In each stage, the major cell types are labeled. The bottom part shows a micrograph of a secondary follicle and the major parts are labeled.

Figure 4. Click for a larger image. (a) The maturation of a follicle is shown in a clockwise direction proceeding from the primordial follicles. FSH stimulates the growth of a tertiary follicle, and LH stimulates the production of estrogen by granulosa and theca cells. Once the follicle is mature, it ruptures and releases the oocyte. Cells remaining in the follicle then develop into the corpus luteum. (b) In this electron micrograph of a secondary follicle, the oocyte, theca cells (thecae folliculi), and developing antrum are clearly visible. EM × 1100. (Micrograph provided by the Regents of University of Michigan Medical School © 2012)

Hormonal Control of the Ovarian Cycle

The process of development that we have just described, from primordial follicle to early tertiary follicle, takes approximately two months in humans. The final stages of development of a small cohort of tertiary follicles, ending with ovulation of a secondary oocyte, occur over a course of approximately 28 days. These changes are regulated by many of the same hormones that regulate the male reproductive system, including GnRH, LH, and FSH.

As in men, the hypothalamus produces GnRH, a hormone that signals the anterior pituitary gland to produce the gonadotropins FSH and LH. These gonadotropins leave the pituitary and travel through the bloodstream to the ovaries, where they bind to receptors on the granulosa and theca cells of the follicles. FSH stimulates the follicles to grow (hence its name of follicle-stimulating hormone), and the five or six tertiary follicles expand in diameter. The release of LH also stimulates the granulosa and theca cells of the follicles to produce the sex steroid hormone estradiol, a type of estrogen. This phase of the ovarian cycle, when the tertiary follicles are growing and secreting estrogen, is known as the follicular phase.

The more granulosa and theca cells a follicle has (that is, the larger and more developed it is), the more estrogen it will produce in response to LH stimulation. As a result of these large follicles producing large amounts of estrogen, systemic plasma estrogen concentrations increase. Following a classic negative feedback loop, the high concentrations of estrogen will stimulate the hypothalamus and pituitary to reduce the production of GnRH, LH, and FSH. Because the large tertiary follicles require FSH to grow and survive at this point, this decline in FSH caused by negative feedback leads most of them to die (atresia). Typically only one follicle, now called the dominant follicle, will survive this reduction in FSH, and this follicle will be the one that releases an oocyte. Scientists have studied many factors that lead to a particular follicle becoming dominant: size, the number of granulosa cells, and the number of FSH receptors on those granulosa cells all contribute to a follicle becoming the one surviving dominant follicle.

This figure shows three flowcharts. The flowchart on the top left shows the hormonal regulation of the follicular phase. The flowchart on the top right shows the hormonal regulation of the ovulation phase. The bottom flowchart shows the hormonal regulation of luteal phase.

Figure 5. Click for a larger image. The hypothalamus and pituitary gland regulate the ovarian cycle and ovulation. GnRH activates the anterior pituitary to produce LH and FSH, which stimulate the production of estrogen and progesterone by the ovaries.

When only the one dominant follicle remains in the ovary, it again begins to secrete estrogen. It produces more estrogen than all of the developing follicles did together before the negative feedback occurred. It produces so much estrogen that the normal negative feedback doesn’t occur. Instead, these extremely high concentrations of systemic plasma estrogen trigger a regulatory switch in the anterior pituitary that responds by secreting large amounts of LH and FSH into the bloodstream. The positive feedback loop by which more estrogen triggers release of more LH and FSH only occurs at this point in the cycle.

It is this large burst of LH (called the LH surge) that leads to ovulation of the dominant follicle. The LH surge induces many changes in the dominant follicle, including stimulating the resumption of meiosis of the primary oocyte to a secondary oocyte. As noted earlier, the polar body that results from unequal cell division simply degrades. The LH surge also triggers proteases (enzymes that cleave proteins) to break down structural proteins in the ovary wall on the surface of the bulging dominant follicle. This degradation of the wall, combined with pressure from the large, fluid-filled antrum, results in the expulsion of the oocyte surrounded by granulosa cells into the peritoneal cavity. This release is ovulation.

In the next section, you will follow the ovulated oocyte as it travels toward the uterus, but there is one more important event that occurs in the ovarian cycle. The surge of LH also stimulates a change in the granulosa and theca cells that remain in the follicle after the oocyte has been ovulated. This change is called luteinization (recall that the full name of LH is luteinizing hormone), and it transforms the collapsed follicle into a new endocrine structure called the corpus luteum , a term meaning “yellowish body”. Instead of estrogen, the luteinized granulosa and theca cells of the corpus luteum begin to produce large amounts of the sex steroid hormone progesterone, a hormone that is critical for the establishment and maintenance of pregnancy. Progesterone triggers negative feedback at the hypothalamus and pituitary, which keeps GnRH, LH, and FSH secretions low, so no new dominant follicles develop at this time.

The post-ovulatory phase of progesterone secretion is known as the luteal phase of the ovarian cycle. If pregnancy does not occur within 10 to 12 days, the corpus luteum will stop secreting progesterone and degrade into the corpus albicans , a nonfunctional “whitish body” that will disintegrate in the ovary over a period of several months. During this time of reduced progesterone secretion, FSH and LH are once again stimulated, and the follicular phase begins again with a new cohort of early tertiary follicles beginning to grow and secrete estrogen.

The Uterine Tubes

The uterine tubes (also called fallopian tubes or oviducts) serve as the conduit of the oocyte from the ovary to the uterus. Each of the two uterine tubes is close to, but not directly connected to, the ovary and divided into sections. The isthmus is the narrow medial end of each uterine tube that is connected to the uterus. The wide distal infundibulum flares out with slender, finger-like projections called fimbriae . The middle region of the tube, called the ampulla , is where fertilization often occurs. The uterine tubes also have three layers: an outer serosa, a middle smooth muscle layer, and an inner mucosal layer. In addition to its mucus-secreting cells, the inner mucosa contains ciliated cells that beat in the direction of the uterus, producing a current that will be critical to move the oocyte.

Following ovulation, the secondary oocyte surrounded by a few granulosa cells is released into the peritoneal cavity. The nearby uterine tube, either left or right, receives the oocyte. Unlike sperm, oocytes lack flagella, and therefore cannot move on their own. So how do they travel into the uterine tube and toward the uterus? High concentrations of estrogen that occur around the time of ovulation induce contractions of the smooth muscle along the length of the uterine tube. These contractions occur every 4 to 8 seconds, and the result is a coordinated movement that sweeps the surface of the ovary and the pelvic cavity. Current flowing toward the uterus is generated by coordinated beating of the cilia that line the outside and lumen of the length of the uterine tube. These cilia beat more strongly in response to the high estrogen concentrations that occur around the time of ovulation. As a result of these mechanisms, the oocyte–granulosa cell complex is pulled into the interior of the tube. Once inside, the muscular contractions and beating cilia move the oocyte slowly toward the uterus. When fertilization does occur, sperm typically meet the egg while it is still moving through the ampulla.

Practice Question

Watch this video to observe ovulation and its initiation in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube?

If the oocyte is successfully fertilized, the resulting zygote will begin to divide into two cells, then four, and so on, as it makes its way through the uterine tube and into the uterus. There, it will implant and continue to grow. If the egg is not fertilized, it will simply degrade—either in the uterine tube or in the uterus, where it may be shed with the next menstrual period.

This diagram shows the uterus and ovaries in the center. To the left is a micrograph showing the ultrastructure of the ovaries and to the right is a micrograph showing the ultrastructure of the uterus.

Figure 6. This anterior view shows the relationship of the ovaries, uterine tubes (oviducts), and uterus. Sperm enter through the vagina, and fertilization of an ovulated oocyte usually occurs in the distal uterine tube. From left to right, LM × 400, LM × 20. (Micrographs provided by the Regents of University of Michigan Medical School © 2012)

The open-ended structure of the uterine tubes can have significant health consequences if bacteria or other contagions enter through the vagina and move through the uterus, into the tubes, and then into the pelvic cavity. If this is left unchecked, a bacterial infection (sepsis) could quickly become life-threatening. The spread of an infection in this manner is of special concern when unskilled practitioners perform abortions in non-sterile conditions. Sepsis is also associated with sexually transmitted bacterial infections, especially gonorrhea and chlamydia. These increase a woman’s risk for pelvic inflammatory disease (PID), infection of the uterine tubes or other reproductive organs. Even when resolved, PID can leave scar tissue in the tubes, leading to infertility.

Watch this series of videos to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation?

The Uterus and Cervix

The uterus is the muscular organ that nourishes and supports the growing embryo. Its average size is approximately 5 cm wide by 7 cm long (approximately 2 in by 3 in) when a female is not pregnant. It has three sections. The portion of the uterus superior to the opening of the uterine tubes is called the fundus . The middle section of the uterus is called the body of uterus (or corpus). The cervix is the narrow inferior portion of the uterus that projects into the vagina. The cervix produces mucus secretions that become thin and stringy under the influence of high systemic plasma estrogen concentrations, and these secretions can facilitate sperm movement through the reproductive tract.

Several ligaments maintain the position of the uterus within the abdominopelvic cavity. The broad ligament is a fold of peritoneum that serves as a primary support for the uterus, extending laterally from both sides of the uterus and attaching it to the pelvic wall. The round ligament attaches to the uterus near the uterine tubes, and extends to the labia majora. Finally, the uterosacral ligament stabilizes the uterus posteriorly by its connection from the cervix to the pelvic wall.

The wall of the uterus is made up of three layers. The most superficial layer is the serous membrane, or perimetrium , which consists of epithelial tissue that covers the exterior portion of the uterus. The middle layer, or myometrium , is a thick layer of smooth muscle responsible for uterine contractions. Most of the uterus is myometrial tissue, and the muscle fibers run horizontally, vertically, and diagonally, allowing the powerful contractions that occur during labor and the less powerful contractions (or cramps) that help to expel menstrual blood during a woman’s period. Anteriorly directed myometrial contractions also occur near the time of ovulation, and are thought to possibly facilitate the transport of sperm through the female reproductive tract.

The innermost layer of the uterus is called the endometrium . The endometrium contains a connective tissue lining, the lamina propria, which is covered by epithelial tissue that lines the lumen. Structurally, the endometrium consists of two layers: the stratum basalis and the stratum functionalis (the basal and functional layers). The stratum basalis layer is part of the lamina propria and is adjacent to the myometrium; this layer does not shed during menses. In contrast, the thicker stratum functionalis layer contains the glandular portion of the lamina propria and the endothelial tissue that lines the uterine lumen. It is the stratum functionalis that grows and thickens in response to increased levels of estrogen and progesterone. In the luteal phase of the menstrual cycle, special branches off of the uterine artery called spiral arteries supply the thickened stratum functionalis. This inner functional layer provides the proper site of implantation for the fertilized egg, and—should fertilization not occur—it is only the stratum functionalis layer of the endometrium that sheds during menstruation.

Recall that during the follicular phase of the ovarian cycle, the tertiary follicles are growing and secreting estrogen. At the same time, the stratum functionalis of the endometrium is thickening to prepare for a potential implantation. The post-ovulatory increase in progesterone, which characterizes the luteal phase, is key for maintaining a thick stratum functionalis. As long as a functional corpus luteum is present in the ovary, the endometrial lining is prepared for implantation. Indeed, if an embryo implants, signals are sent to the corpus luteum to continue secreting progesterone to maintain the endometrium, and thus maintain the pregnancy. If an embryo does not implant, no signal is sent to the corpus luteum and it degrades, ceasing progesterone production and ending the luteal phase. Without progesterone, the endometrium thins and, under the influence of prostaglandins, the spiral arteries of the endometrium constrict and rupture, preventing oxygenated blood from reaching the endometrial tissue. As a result, endometrial tissue dies and blood, pieces of the endometrial tissue, and white blood cells are shed through the vagina during menstruation, or the menses . The first menses after puberty, called menarche , can occur either before or after the first ovulation.

The Menstrual Cycle

Now that we have discussed the maturation of the cohort of tertiary follicles in the ovary, the build-up and then shedding of the endometrial lining in the uterus, and the function of the uterine tubes and vagina, we can put everything together to talk about the three phases of the menstrual cycle —the series of changes in which the uterine lining is shed, rebuilds, and prepares for implantation.

The timing of the menstrual cycle starts with the first day of menses, referred to as day one of a woman’s period. Cycle length is determined by counting the days between the onset of bleeding in two subsequent cycles. Because the average length of a woman’s menstrual cycle is 28 days, this is the time period used to identify the timing of events in the cycle. However, the length of the menstrual cycle varies among women, and even in the same woman from one cycle to the next, typically from 21 to 32 days.

Just as the hormones produced by the granulosa and theca cells of the ovary “drive” the follicular and luteal phases of the ovarian cycle, they also control the three distinct phases of the menstrual cycle. These are the menses phase, the proliferative phase, and the secretory phase.

Menses Phase

The menses phase of the menstrual cycle is the phase during which the lining is shed; that is, the days that the woman menstruates. Although it averages approximately five days, the menses phase can last from 2 to 7 days, or longer. As shown in Figure 7, the menses phase occurs during the early days of the follicular phase of the ovarian cycle, when progesterone, FSH, and LH levels are low. Recall that progesterone concentrations decline as a result of the degradation of the corpus luteum, marking the end of the luteal phase. This decline in progesterone triggers the shedding of the stratum functionalis of the endometrium.

The top panel of this image shows the stages in the follicular phase and how one follicle is selected at the end of this phase. The middle part of this image shows the ovarian cycle phases and the uterine cycle phases. The bottom panel shows the levels of different hormones as a function of time.

Figure 7. Click for a larger image. The correlation of the hormone levels and their effects on the female reproductive system is shown in this timeline of the ovarian and menstrual cycles. The menstrual cycle begins at day one with the start of menses. Ovulation occurs around day 14 of a 28-day cycle, triggered by the LH surge.

Proliferative Phase

Once menstrual flow ceases, the endometrium begins to proliferate again, marking the beginning of the proliferative phase of the menstrual cycle. It occurs when the granulosa and theca cells of the tertiary follicles begin to produce increased amounts of estrogen. These rising estrogen concentrations stimulate the endometrial lining to rebuild.

Recall that the high estrogen concentrations will eventually lead to a decrease in FSH as a result of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback—which occurs with the elevated estrogen production from the dominant follicle—then stimulates the LH surge that will trigger ovulation. In a typical 28-day menstrual cycle, ovulation occurs on day 14. Ovulation marks the end of the proliferative phase as well as the end of the follicular phase.

Secretory Phase

In addition to prompting the LH surge, high estrogen levels increase the uterine tube contractions that facilitate the pick-up and transfer of the ovulated oocyte. High estrogen levels also slightly decrease the acidity of the vagina, making it more hospitable to sperm. In the ovary, the luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum, marking the beginning of the luteal phase of the ovarian cycle. In the uterus, progesterone from the corpus luteum begins the secretory phase of the menstrual cycle, in which the endometrial lining prepares for implantation. Over the next 10 to 12 days, the endometrial glands secrete a fluid rich in glycogen. If fertilization has occurred, this fluid will nourish the ball of cells now developing from the zygote. At the same time, the spiral arteries develop to provide blood to the thickened stratum functionalis.

If no pregnancy occurs within approximately 10 to 12 days, the corpus luteum will degrade into the corpus albicans. Levels of both estrogen and progesterone will fall, and the endometrium will grow thinner. Prostaglandins will be secreted that cause constriction of the spiral arteries, reducing oxygen supply. The endometrial tissue will die, resulting in menses—or the first day of the next cycle.

Disorders of the Female Reproductive System

Research over many years has confirmed that cervical cancer is most often caused by a sexually transmitted infection with human papillomavirus (HPV). There are over 100 related viruses in the HPV family, and the characteristics of each strain determine the outcome of the infection. In all cases, the virus enters body cells and uses its own genetic material to take over the host cell’s metabolic machinery and produce more virus particles.

HPV infections are common in both men and women. Indeed, a recent study determined that 42.5 percent of females had HPV at the time of testing. These women ranged in age from 14 to 59 years and differed in race, ethnicity, and number of sexual partners. Of note, the prevalence of HPV infection was 53.8 percent among women aged 20 to 24 years, the age group with the highest infection rate.

HPV strains are classified as high or low risk according to their potential to cause cancer. Though most HPV infections do not cause disease, the disruption of normal cellular functions in the low-risk forms of HPV can cause the male or female human host to develop genital warts. Often, the body is able to clear an HPV infection by normal immune responses within 2 years. However, the more serious, high-risk infection by certain types of HPV can result in cancer of the cervix. Infection with either of the cancer-causing variants HPV 16 or HPV 18 has been linked to more than 70 percent of all cervical cancer diagnoses. Although even these high-risk HPV strains can be cleared from the body over time, infections persist in some individuals. If this happens, the HPV infection can influence the cells of the cervix to develop precancerous changes.

Risk factors for cervical cancer include having unprotected sex; having multiple sexual partners; a first sexual experience at a younger age, when the cells of the cervix are not fully mature; failure to receive the HPV vaccine; a compromised immune system; and smoking. The risk of developing cervical cancer is doubled with cigarette smoking.

The left panel shows cell cycle. An arrow from the G2 phase leads to the right panel. The top half of the right panel describes the next steps in the absence of HPV and the bottom half describes the next steps in the presence of HPV.

Figure 8. In most cases, cells infected with the HPV virus heal on their own. In some cases, however, the virus continues to spread and becomes an invasive cancer.

When the high-risk types of HPV enter a cell, two viral proteins are used to neutralize proteins that the host cells use as checkpoints in the cell cycle. The best studied of these proteins is p53. In a normal cell, p53 detects DNA damage in the cell’s genome and either halts the progression of the cell cycle—allowing time for DNA repair to occur—or initiates apoptosis. Both of these processes prevent the accumulation of mutations in a cell’s genome. High-risk HPV can neutralize p53, keeping the cell in a state in which fast growth is possible and impairing apoptosis, allowing mutations to accumulate in the cellular DNA.

The prevalence of cervical cancer in the United States is very low because of regular screening exams called pap smears. Pap smears sample cells of the cervix, allowing the detection of abnormal cells. If pre-cancerous cells are detected, there are several highly effective techniques that are currently in use to remove them before they pose a danger. However, women in developing countries often do not have access to regular pap smears. As a result, these women account for as many as 80 percent of the cases of cervical cancer worldwide.

In 2006, the first vaccine against the high-risk types of HPV was approved. There are now two HPV vaccines available: Gardasil ® and Cervarix ® . Whereas these vaccines were initially only targeted for women, because HPV is sexually transmitted, both men and women require vaccination for this approach to achieve its maximum efficacy. A recent study suggests that the HPV vaccine has cut the rates of HPV infection by the four targeted strains at least in half. Unfortunately, the high cost of manufacturing the vaccine is currently limiting access to many women worldwide.

The Breasts

Whereas the breasts are located far from the other female reproductive organs, they are considered accessory organs of the female reproductive system. The function of the breasts is to supply milk to an infant in a process called lactation. The external features of the breast include a nipple surrounded by a pigmented areola , whose coloration may deepen during pregnancy. The areola is typically circular and can vary in size from 25 to 100 mm in diameter. The areolar region is characterized by small, raised areolar glands that secrete lubricating fluid during lactation to protect the nipple from chafing. When a baby nurses, or draws milk from the breast, the entire areolar region is taken into the mouth.

Breast milk is produced by the mammary glands , which are modified sweat glands. The milk itself exits the breast through the nipple via 15 to 20 lactiferous ducts that open on the surface of the nipple. These lactiferous ducts each extend to a lactiferous sinus that connects to a glandular lobe within the breast itself that contains groups of milk-secreting cells in clusters called alveoli . The clusters can change in size depending on the amount of milk in the alveolar lumen. Once milk is made in the alveoli, stimulated myoepithelial cells that surround the alveoli contract to push the milk to the lactiferous sinuses. From here, the baby can draw milk through the lactiferous ducts by suckling. The lobes themselves are surrounded by fat tissue, which determines the size of the breast; breast size differs between individuals and does not affect the amount of milk produced. Supporting the breasts are multiple bands of connective tissue called suspensory ligaments that connect the breast tissue to the dermis of the overlying skin.

This figure shows the anatomy of the breast. The left panel shows the front view and the right panel shows the side view. The main parts are labeled.

Figure 9. During lactation, milk moves from the alveoli through the lactiferous ducts to the nipple.

During the normal hormonal fluctuations in the menstrual cycle, breast tissue responds to changing levels of estrogen and progesterone, which can lead to swelling and breast tenderness in some individuals, especially during the secretory phase. If pregnancy occurs, the increase in hormones leads to further development of the mammary tissue and enlargement of the breasts.

Hormonal Birth Control

Birth control pills take advantage of the negative feedback system that regulates the ovarian and menstrual cycles to stop ovulation and prevent pregnancy. Typically they work by providing a constant level of both estrogen and progesterone, which negatively feeds back onto the hypothalamus and pituitary, thus preventing the release of FSH and LH. Without FSH, the follicles do not mature, and without the LH surge, ovulation does not occur. Although the estrogen in birth control pills does stimulate some thickening of the endometrial wall, it is reduced compared with a normal cycle and is less likely to support implantation.

Some birth control pills contain 21 active pills containing hormones, and 7 inactive pills (placebos). The decline in hormones during the week that the woman takes the placebo pills triggers menses, although it is typically lighter than a normal menstrual flow because of the reduced endometrial thickening. Newer types of birth control pills have been developed that deliver low-dose estrogens and progesterone for the entire cycle (these are meant to be taken 365 days a year), and menses never occurs. While some women prefer to have the proof of a lack of pregnancy that a monthly period provides, menstruation every 28 days is not required for health reasons, and there are no reported adverse effects of not having a menstrual period in an otherwise healthy individual.

Because birth control pills function by providing constant estrogen and progesterone levels and disrupting negative feedback, skipping even just one or two pills at certain points of the cycle (or even being several hours late taking the pill) can lead to an increase in FSH and LH and result in ovulation. It is important, therefore, that the woman follow the directions on the birth control pill package to successfully prevent pregnancy.

Aging and the Female Reproductive System

Female fertility (the ability to conceive) peaks when women are in their twenties, and is slowly reduced until a women reaches 35 years of age. After that time, fertility declines more rapidly, until it ends completely at the end of menopause. Menopause is the cessation of the menstrual cycle that occurs as a result of the loss of ovarian follicles and the hormones that they produce. A woman is considered to have completed menopause if she has not menstruated in a full year. After that point, she is considered postmenopausal. The average age for this change is consistent worldwide at between 50 and 52 years of age, but it can normally occur in a woman’s forties, or later in her fifties. Poor health, including smoking, can lead to earlier loss of fertility and earlier menopause.

As a woman reaches the age of menopause, depletion of the number of viable follicles in the ovaries due to atresia affects the hormonal regulation of the menstrual cycle. During the years leading up to menopause, there is a decrease in the levels of the hormone inhibin, which normally participates in a negative feedback loop to the pituitary to control the production of FSH. The menopausal decrease in inhibin leads to an increase in FSH. The presence of FSH stimulates more follicles to grow and secrete estrogen. Because small, secondary follicles also respond to increases in FSH levels, larger numbers of follicles are stimulated to grow; however, most undergo atresia and die. Eventually, this process leads to the depletion of all follicles in the ovaries, and the production of estrogen falls off dramatically. It is primarily the lack of estrogens that leads to the symptoms of menopause.

The earliest changes occur during the menopausal transition, often referred to as peri-menopause, when a women’s cycle becomes irregular but does not stop entirely. Although the levels of estrogen are still nearly the same as before the transition, the level of progesterone produced by the corpus luteum is reduced. This decline in progesterone can lead to abnormal growth, or hyperplasia, of the endometrium. This condition is a concern because it increases the risk of developing endometrial cancer. Two harmless conditions that can develop during the transition are uterine fibroids, which are benign masses of cells, and irregular bleeding. As estrogen levels change, other symptoms that occur are hot flashes and night sweats, trouble sleeping, vaginal dryness, mood swings, difficulty focusing, and thinning of hair on the head along with the growth of more hair on the face. Depending on the individual, these symptoms can be entirely absent, moderate, or severe.

After menopause, lower amounts of estrogens can lead to other changes. Cardiovascular disease becomes as prevalent in women as in men, possibly because estrogens reduce the amount of cholesterol in the blood vessels. When estrogen is lacking, many women find that they suddenly have problems with high cholesterol and the cardiovascular issues that accompany it. Osteoporosis is another problem because bone density decreases rapidly in the first years after menopause. The reduction in bone density leads to a higher incidence of fractures.

Hormone therapy (HT), which employs medication (synthetic estrogens and progestins) to increase estrogen and progestin levels, can alleviate some of the symptoms of menopause. In 2002, the Women’s Health Initiative began a study to observe women for the long-term outcomes of hormone replacement therapy over 8.5 years. However, the study was prematurely terminated after 5.2 years because of evidence of a higher than normal risk of breast cancer in patients taking estrogen-only HT. The potential positive effects on cardiovascular disease were also not realized in the estrogen-only patients. The results of other hormone replacement studies over the last 50 years, including a 2012 study that followed over 1,000 menopausal women for 10 years, have shown cardiovascular benefits from estrogen and no increased risk for cancer. Some researchers believe that the age group tested in the 2002 trial may have been too old to benefit from the therapy, thus skewing the results. In the meantime, intense debate and study of the benefits and risks of replacement therapy is ongoing. Current guidelines approve HT for the reduction of hot flashes or flushes, but this treatment is generally only considered when women first start showing signs of menopausal changes, is used in the lowest dose possible for the shortest time possible (5 years or less), and it is suggested that women on HT have regular pelvic and breast exams.

Chapter Review

The external female genitalia are collectively called the vulva. The vagina is the pathway into and out of the uterus. The man’s penis is inserted into the vagina to deliver sperm, and the baby exits the uterus through the vagina during childbirth.

The ovaries produce oocytes, the female gametes, in a process called oogenesis. As with spermatogenesis, meiosis produces the haploid gamete (in this case, an ovum); however, it is completed only in an oocyte that has been penetrated by a sperm. In the ovary, an oocyte surrounded by supporting cells is called a follicle. In folliculogenesis, primordial follicles develop into primary, secondary, and tertiary follicles. Early tertiary follicles with their fluid-filled antrum will be stimulated by an increase in FSH, a gonadotropin produced by the anterior pituitary, to grow in the 28-day ovarian cycle. Supporting granulosa and theca cells in the growing follicles produce estrogens, until the level of estrogen in the bloodstream is high enough that it triggers negative feedback at the hypothalamus and pituitary. This results in a reduction of FSH and LH, and most tertiary follicles in the ovary undergo atresia (they die). One follicle, usually the one with the most FSH receptors, survives this period and is now called the dominant follicle. The dominant follicle produces more estrogen, triggering positive feedback and the LH surge that will induce ovulation. Following ovulation, the granulosa cells of the empty follicle luteinize and transform into the progesterone-producing corpus luteum. The ovulated oocyte with its surrounding granulosa cells is picked up by the infundibulum of the uterine tube, and beating cilia help to transport it through the tube toward the uterus. Fertilization occurs within the uterine tube, and the final stage of meiosis is completed.

The uterus has three regions: the fundus, the body, and the cervix. It has three layers: the outer perimetrium, the muscular myometrium, and the inner endometrium. The endometrium responds to estrogen released by the follicles during the menstrual cycle and grows thicker with an increase in blood vessels in preparation for pregnancy. If the egg is not fertilized, no signal is sent to extend the life of the corpus luteum, and it degrades, stopping progesterone production. This decline in progesterone results in the sloughing of the inner portion of the endometrium in a process called menses, or menstruation.

The breasts are accessory sexual organs that are utilized after the birth of a child to produce milk in a process called lactation. Birth control pills provide constant levels of estrogen and progesterone to negatively feed back on the hypothalamus and pituitary, and suppress the release of FSH and LH, which inhibits ovulation and prevents pregnancy.

Critical Thinking Questions

Follow the path of ejaculated sperm from the vagina to the oocyte. Include all structures of the female reproductive tract that the sperm must swim through to reach the egg.
Identify some differences between meiosis in men and women.
Explain the hormonal regulation of the phases of the menstrual cycle.
Endometriosis is a disorder in which endometrial cells implant and proliferate outside of the uterus—in the uterine tubes, on the ovaries, or even in the pelvic cavity. Offer a theory as to why endometriosis increases a woman’s risk of infertility.
The sperm must swim upward in the vagina, through the cervix, and then through the body of the uterus to one or the other of the two uterine tubes. Fertilization generally occurs in the uterine tube.
Meiosis in the man results in four viable haploid sperm, whereas meiosis in the woman results in a secondary oocyte and, upon completion following fertilization by a sperm, one viable haploid ovum with abundant cytoplasm and up to three polar bodies with little cytoplasm that are destined to die.
As a result of the degradation of the corpus luteum, a decline in progesterone concentrations triggers the shedding of the endometrial lining, marking the menses phase of the menstrual cycle. Low progesterone levels also reduce the negative feedback that had been occurring at the hypothalamus and pituitary, and result in the release of GnRH and, subsequently, FSH and LH. FSH stimulates tertiary follicles to grow and granulosa and theca cells begin to produce increased amounts of estrogen. High estrogen concentrations stimulate the endometrial lining to rebuild, marking the proliferative phase of the menstrual cycle. The high estrogen concentrations will eventually lead to a decrease in FSH because of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback that occurs with elevated estrogen production from the dominant follicle stimulates the LH surge that will trigger ovulation. The luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum. Progesterone from the corpus luteum causes the endometrium to prepare for implantation, in part by secreting nutrient-rich fluid. This marks the secretory phase of the menstrual cycle. Finally, in a non-fertile cycle, the corpus luteum will degrade and menses will occur.
Endometrial tissue proliferating outside of the endometrium—for example, in the uterine tubes, on the ovaries, or within the pelvic cavity—could block the passage of sperm, ovulated oocytes, or a zygote, thus reducing fertility.

alveoli: (of the breast) milk-secreting cells in the mammary gland

ampulla: (of the uterine tube) middle portion of the uterine tube in which fertilization often occurs

antrum: fluid-filled chamber that characterizes a mature tertiary (antral) follicle

areola: highly pigmented, circular area surrounding the raised nipple and containing areolar glands that secrete fluid important for lubrication during suckling

Bartholin’s glands: (also, greater vestibular glands) glands that produce a thick mucus that maintains moisture in the vulva area; also referred to as the greater vestibular glands

body of uterus: middle section of the uterus

broad ligament: wide ligament that supports the uterus by attaching laterally to both sides of the uterus and pelvic wall

cervix: elongate inferior end of the uterus where it connects to the vagina

clitoris: (also, glans clitoris) nerve-rich area of the vulva that contributes to sexual sensation during intercourse

corpus albicans: nonfunctional structure remaining in the ovarian stroma following structural and functional regression of the corpus luteum

corpus luteum: transformed follicle after ovulation that secretes progesterone

endometrium: inner lining of the uterus, part of which builds up during the secretory phase of the menstrual cycle and then sheds with menses

fimbriae: fingerlike projections on the distal uterine tubes

follicle: ovarian structure of one oocyte and surrounding granulosa (and later theca) cells

folliculogenesis: development of ovarian follicles from primordial to tertiary under the stimulation of gonadotropins

fundus: (of the uterus) domed portion of the uterus that is superior to the uterine tubes

granulosa cells: supportive cells in the ovarian follicle that produce estrogen

hymen: membrane that covers part of the opening of the vagina

infundibulum: (of the uterine tube) wide, distal portion of the uterine tube terminating in fimbriae

isthmus: narrow, medial portion of the uterine tube that joins the uterus

labia majora: hair-covered folds of skin located behind the mons pubis

labia minora: thin, pigmented, hairless flaps of skin located medial and deep to the labia majora

lactiferous ducts: ducts that connect the mammary glands to the nipple and allow for the transport of milk

lactiferous sinus: area of milk collection between alveoli and lactiferous duct

mammary glands: glands inside the breast that secrete milk

menarche: first menstruation in a pubertal female

menses: shedding of the inner portion of the endometrium out though the vagina; also referred to as menstruation

menses phase: phase of the menstrual cycle in which the endometrial lining is shed

menstrual cycle: approximately 28-day cycle of changes in the uterus consisting of a menses phase, a proliferative phase, and a secretory phase

mons pubis: mound of fatty tissue located at the front of the vulva

myometrium: smooth muscle layer of uterus that allows for uterine contractions during labor and expulsion of menstrual blood

oocyte: cell that results from the division of the oogonium and undergoes meiosis I at the LH surge and meiosis II at fertilization to become a haploid ovum

oogenesis: process by which oogonia divide by mitosis to primary oocytes, which undergo meiosis to produce the secondary oocyte and, upon fertilization, the ovum

oogonia: ovarian stem cells that undergo mitosis during female fetal development to form primary oocytes

ovarian cycle: approximately 28-day cycle of changes in the ovary consisting of a follicular phase and a luteal phase

ovaries: female gonads that produce oocytes and sex steroid hormones (notably estrogen and progesterone)

ovulation: release of a secondary oocyte and associated granulosa cells from an ovary

ovum: haploid female gamete resulting from completion of meiosis II at fertilization

perimetrium: outer epithelial layer of uterine wall

polar body: smaller cell produced during the process of meiosis in oogenesis

primary follicles: ovarian follicles with a primary oocyte and one layer of cuboidal granulosa cells

primordial follicles: least developed ovarian follicles that consist of a single oocyte and a single layer of flat (squamous) granulosa cells

proliferative phase: phase of the menstrual cycle in which the endometrium proliferates

rugae: (of the vagina) folds of skin in the vagina that allow it to stretch during intercourse and childbirth

secondary follicles: ovarian follicles with a primary oocyte and multiple layers of granulosa cells

secretory phase: phase of the menstrual cycle in which the endometrium secretes a nutrient-rich fluid in preparation for implantation of an embryo

suspensory ligaments: bands of connective tissue that suspend the breast onto the chest wall by attachment to the overlying dermis

tertiary follicles: (also, antral follicles) ovarian follicles with a primary or secondary oocyte, multiple layers of granulosa cells, and a fully formed antrum

theca cells: estrogen-producing cells in a maturing ovarian follicle

uterine tubes: (also, fallopian tubes or oviducts) ducts that facilitate transport of an ovulated oocyte to the uterus

uterus: muscular hollow organ in which a fertilized egg develops into a fetus

vagina: tunnel-like organ that provides access to the uterus for the insertion of semen and from the uterus for the birth of a baby

vulva: external female genitalia

Anatomy & Physiology. Provided by : OpenStax CNX. Located at : http://cnx.org/contents/[email protected] . License : CC BY: Attribution . License Terms : Download for free at http://cnx.org/contents/[email protected]

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22.5: Laboratory Activities and Assignment

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Rosanna Hartline
West Hills College Lemoore

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Laboratory Activities and Assignment

Part 1: review of the reproductive systems.

1. Label the structures listed below on the diagram of the female genitalia below.

2. Label the structures listed below on the diagram of internal female genitalia below.

3. Label the structures listed below on the diagram of the external female genitalia.

4. Label the structures listed below on the diagram of the male genitalia below.

5. Label the structures listed below on the diagram of the male genitalia below.

7. On the figure above, number the structures spermatozoa pass through to exit the male reproductive system from where spermatids are created (#1) to the point where they exit the body.

8. On the figure above, add a star (*) next to the name of each structure that contributes to semen.

9. Label the structures listed below on the diagram of the male genitalia below.

10.Match the structure listed in the table below with its corresponding description.

Part 2: Histology of the Reproductive Systems

Obtain the slides listed below that are available for today’s lab.
Focus on each sample and identify the structures listed for each type of tissue.
Indicate the total magnification you make each illustration at in the space provided.
Illustrate each tissue you observe with the microscope at the magnification you listed.
Label each illustration with the structures listed for each.

More than one illustration at more than one magnification will be required to illustrate and label all structures

Label the tissue with: serosa, medulla, cortex, tunica albuginea, follicles, primordial follicles, primary follicles, secondary follicles, antral spaces, primary oocytes, corpus luteum, atretic follicles

More than one illustration at different magnifications and possibly of different slides will be necessary to illustrate and label all structures listed.

Label the tissue with: testis, epididymis, vas deferens, tunica albuginea, tunica vaginalis, seminiferous tubules, lumen of seminiferous tubule, spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid

Part 3: Reproductive Systems Laboratory Activities

Labeling male reproductive anatomical model(s).

Use the anatomical model(s) provided to your group.
As a group, identify the structures listed below.
Write each of the following structures on masking tape or labeling tape (with correct spelling) and stick onto the model to label each structure.

4. When you are done, ask your instructor to verify the labeling is correct.

Instructor Signature Confirming Correct Labeling: ___________________

5. Take a photo of your anatomical model for future reference for studying.

Labeling Female Reproductive Anatomical Model(s)

Attributions, part 1: review of reproductive systems.

"Anatomy and Physiology Lab Homework" by Laird C Sheldahl is licensed under CC BY-SA 4.0
"Female anatomy with g-spot-nb.svg" by Tsaitgaist is licensed under CC BY-SA 3.0
"Gray's Anatomy plates" by Henry Vandyke Carte is in the Public Domain
"Human Anatomy Lab Manual" by Malgosia Wilk-Blaszczak , Mavs Open Press , University of Texas at Arlington is licensed under CC BY 4.0
"Male reproductive system.png" by User:Ningyou is licensed under CC BY-SA 3.0
"Male reproductive tract.png" by Sheldahl is licensed under CC BY-SA 4.0
"BIOL 250 Human Anatomy Lab Manual SU 19" by Yancy Aquino , Skyline College is licensed under CC BY-NC-SA 4.0

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19.3: Anatomy and Physiology of the Female Reproductive System

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Simantini Karve
Skyline College

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Learning Objectives

Describe the structure and function of the organs of the female reproductive system
List the steps of oogenesis
Describe the hormonal changes that occur during the ovarian and menstrual cycles
Trace the path of an oocyte from ovary to fertilization

The female reproductive system functions to produce gametes and reproductive hormones, just like the male reproductive system; however, it also has the additional task of supporting the developing fetus and delivering it to the outside world. Unlike its male counterpart, the female reproductive system is located primarily inside the pelvic cavity (Figure \(\PageIndex{1}\)). Recall that the ovaries are the female gonads. The gamete they produce is called an oocyte . We’ll discuss the production of oocytes in detail shortly. First, let’s look at some of the structures of the female reproductive system.

External Female Genitals

The external female reproductive structures are referred to collectively as the vulva (Figure \(\PageIndex{2}\)). The mons pubis is a pad of fat that is located at the anterior, over the pubic bone. After puberty, it becomes covered in pubic hair. The labia majora (labia = “lips”; majora = “larger”) are folds of hair-covered skin that begin just posterior to the mons pubis. The thinner and more pigmented labia minora (labia = “lips”; minora = “smaller”) extend medial to the labia majora. Although they naturally vary in shape and size from woman to woman, the labia minora serve to protect the female urethra and the entrance to the female reproductive tract.

The vagina , shown at the bottom of Figure \(\PageIndex{1}\) and Figure \(\PageIndex{1}\), is a muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth. The outer walls of the anterior and posterior vagina are formed into longitudinal columns, or ridges, and the superior portion of the vagina—called the fornix—meets the protruding uterine cervix. The walls of the vagina are lined with an outer, fibrous adventitia; a middle layer of smooth muscle; and an inner mucous membrane with transverse folds called rugae . Together, the middle and inner layers allow the expansion of the vagina to accommodate intercourse and childbirth. The thin, perforated hymen can partially surround the opening to the vaginal orifice. The hymen can be ruptured with strenuous physical exercise, penile–vaginal intercourse, and childbirth. The Bartholin’s glands and the lesser vestibular glands (located near the clitoris) secrete mucus, which keeps the vestibular area moist.

The ovaries are the female gonads (see Figure \(\PageIndex{1}\)). Paired ovals, they are each about 2 to 3 cm in length, about the size of an almond. The ovaries are located within the pelvic cavity, and are supported by the mesovarium, an extension of the peritoneum that connects the ovaries to the broad ligament . Extending from the mesovarium itself is the suspensory ligament that contains the ovarian blood and lymph vessels. Finally, the ovary itself is attached to the uterus via the ovarian ligament.

The Ovarian Cycle

Gametogenesis in females is called oogenesis . The process begins with the ovarian stem cells, or oogonia (Figure \(\PageIndex{3}\)). Oogonia are formed during fetal development, and divide via mitosis, much like spermatogonia in the testis. Unlike spermatogonia, however, oogonia form primary oocytes in the fetal ovary prior to birth. These primary oocytes are then arrested in this stage of meiosis I, only to resume it years later, beginning at puberty and continuing until the woman is near menopause (the cessation of a woman’s reproductive functions). The number of primary oocytes present in the ovaries declines from one to two million in an infant, to approximately 400,000 at puberty, to zero by the end of menopause.

The initiation of ovulation —the release of an oocyte from the ovary—marks the transition from puberty into reproductive maturity for women. From then on, throughout a woman’s reproductive years, ovulation occurs approximately once every 28 days. Just prior to ovulation, a surge of luteinizing hormone triggers the resumption of meiosis in a primary oocyte. This initiates the transition from primary to secondary oocyte. However, as you can see in Figure \(\PageIndex{3}\), this cell division does not result in two identical cells. Instead, the cytoplasm is divided unequally, and one daughter cell is much larger than the other. This larger cell, the secondary oocyte, eventually leaves the ovary during ovulation. The smaller cell, called the first polar body , may or may not complete meiosis and produce second polar bodies; in either case, it eventually disintegrates. Therefore, even though oogenesis produces up to four cells, only one survives.

Everyday Connections: Mapping Human History with Mitochondrial DNA

Folliculogenesis

Folliculogenesis begins with follicles in a resting state. These small primordial follicles are present in newborn females and are the prevailing follicle type in the adult ovary (Figure \(\PageIndex{4}\)). Primordial follicles have only a single flat layer of support cells, called granulosa cells , that surround the oocyte, and they can stay in this resting state for years—some until right before menopause.

After puberty, a few primordial follicles will respond to a recruitment signal each day, and will join a pool of immature growing follicles called primary follicles . Primary follicles start with a single layer of granulosa cells, but the granulosa cells then become active and transition from a flat or squamous shape to a rounded, cuboidal shape as they increase in size and proliferate. As the granulosa cells divide, the follicles—now called secondary follicles (see Figure \(\PageIndex{4}\))—increase in diameter, adding a new outer layer of connective tissue, blood vessels, and theca cells —cells that work with the granulosa cells to produce estrogens.

Hormonal Control of the Ovarian Cycle

As in men, the hypothalamus produces GnRH, a hormone that signals the anterior pituitary gland to produce the gonadotropins FSH and LH (Figure \(\PageIndex{5}\)). These gonadotropins leave the pituitary and travel through the bloodstream to the ovaries, where they bind to receptors on the granulosa and theca cells of the follicles. FSH stimulates the follicles to grow (hence its name of follicle-stimulating hormone), and the five or six tertiary follicles expand in diameter. The release of LH also stimulates the granulosa and theca cells of the follicles to produce the sex steroid hormone estradiol, a type of estrogen. This phase of the ovarian cycle, when the tertiary follicles are growing and secreting estrogen, is known as the follicular phase.

When only the one dominant follicle remains in the ovary, it again begins to secrete estrogen. It produces more estrogen than all of the developing follicles did together before the negative feedback occurred. It produces so much estrogen that the normal negative feedback doesn’t occur. Instead, these extremely high concentrations of systemic plasma estrogen trigger a regulatory switch in the anterior pituitary that responds by secreting large amounts of LH and FSH into the bloodstream (see Figure \(\PageIndex{5}\)). The positive feedback loop by which more estrogen triggers release of more LH and FSH only occurs at this point in the cycle.

In the next section, you will follow the ovulated oocyte as it travels toward the uterus, but there is one more important event that occurs in the ovarian cycle. The surge of LH also stimulates a change in the granulosa and theca cells that remain in the follicle after the oocyte has been ovulated. This change is called luteinization (recall that the full name of LH is luteinizing hormone), and it transforms the collapsed follicle into a new endocrine structure called the corpus luteum , a term meaning “yellowish body” (see Figure \(\PageIndex{4}\)). Instead of estrogen, the luteinized granulosa and theca cells of the corpus luteum begin to produce large amounts of the sex steroid hormone progesterone, a hormone that is critical for the establishment and maintenance of pregnancy. Progesterone triggers negative feedback at the hypothalamus and pituitary, which keeps GnRH, LH, and FSH secretions low, so no new dominant follicles develop at this time.

The Uterine Tubes

The uterine tubes (also called fallopian tubes or oviducts) serve as the conduit of the oocyte from the ovary to the uterus (Figure \(\PageIndex{6}\)). Each of the two uterine tubes is close to, but not directly connected to, the ovary and divided into sections. The isthmus is the narrow medial end of each uterine tube that is connected to the uterus. The wide distal infundibulum flares out with slender, finger-like projections called fimbriae . The middle region of the tube, called the ampulla , is where fertilization often occurs. The uterine tubes also have three layers: an outer serosa, a middle smooth muscle layer, and an inner mucosal layer. In addition to its mucus-secreting cells, the inner mucosa contains ciliated cells that beat in the direction of the uterus, producing a current that will be critical to move the oocyte.

Figure \(\PageIndex{6}\): Ovaries, uterine tubes, and uterus. This anterior view shows the relationship of the ovaries, uterine tubes (oviducts), and uterus. Sperm enter through the vagina, and fertilization of an ovulated oocyte usually occurs in the distal uterine tube. From left to right, LM × 400, LM × 20. (Micrographs provided by the Regents of University of Michigan Medical School © 2012)

The Uterus and Cervix

The uterus is the muscular organ that nourishes and supports the growing embryo (see Figure \(\PageIndex{6}\)). Its average size is approximately 5 cm wide by 7 cm long (approximately 2 in by 3 in) when a female is not pregnant. It has three sections. The portion of the uterus superior to the opening of the uterine tubes is called the fundus . The middle section of the uterus is called the body of uterus (or corpus). The cervix is the narrow inferior portion of the uterus that projects into the vagina. The cervix produces mucus secretions that become thin and stringy under the influence of high systemic plasma estrogen concentrations, and these secretions can facilitate sperm movement through the reproductive tract.

The Menstrual Cycle

Menses Phase

The menses phase of the menstrual cycle is the phase during which the lining is shed; that is, the days that the woman menstruates. Although it averages approximately five days, the menses phase can last from 2 to 7 days, or longer. As shown in Figure \(\PageIndex{7}\), the menses phase occurs during the early days of the follicular phase of the ovarian cycle, when progesterone, FSH, and LH levels are low. Recall that progesterone concentrations decline as a result of the degradation of the corpus luteum, marking the end of the luteal phase. This decline in progesterone triggers the shedding of the stratum functionalis of the endometrium.

Hormones associated with ovarian and menstrual cycle

Proliferative Phase

Once menstrual flow ceases, the endometrium begins to proliferate again, marking the beginning of the proliferative phase of the menstrual cycle (see Figure \(\PageIndex{7}\)). It occurs when the granulosa and theca cells of the tertiary follicles begin to produce increased amounts of estrogen. These rising estrogen concentrations stimulate the endometrial lining to rebuild.

Secretory Phase

In addition to prompting the LH surge, high estrogen levels increase the uterine tube contractions that facilitate the pick-up and transfer of the ovulated oocyte. High estrogen levels also slightly decrease the acidity of the vagina, making it more hospitable to sperm. In the ovary, the luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum, marking the beginning of the luteal phase of the ovarian cycle. In the uterus, progesterone from the corpus luteum begins the secretory phase of the menstrual cycle, in which the endometrial lining prepares for implantation (see Figure \(\PageIndex{7}\)). Over the next 10 to 12 days, the endometrial glands secrete a fluid rich in glycogen. If fertilization has occurred, this fluid will nourish the ball of cells now developing from the zygote. At the same time, the spiral arteries develop to provide blood to the thickened stratum functionalis.

Disorders of the Female Reproductive System

HPV strains are classified as high or low risk according to their potential to cause cancer. Though most HPV infections do not cause disease, the disruption of normal cellular functions in the low-risk forms of HPV can cause the male or female human host to develop genital warts. Often, the body is able to clear an HPV infection by normal immune responses within 2 years. However, the more serious, high-risk infection by certain types of HPV can result in cancer of the cervix (Figure \(\PageIndex{8}\)). Infection with either of the cancer-causing variants HPV 16 or HPV 18 has been linked to more than 70 percent of all cervical cancer diagnoses. Although even these high-risk HPV strains can be cleared from the body over time, infections persist in some individuals. If this happens, the HPV infection can influence the cells of the cervix to develop precancerous changes.

The Breasts

Whereas the breasts are located far from the other female reproductive organs, they are considered accessory organs of the female reproductive system. The function of the breasts is to supply milk to an infant in a process called lactation. The external features of the breast include a nipple surrounded by a pigmented areola (Figure \(\PageIndex{9}\)), whose coloration may deepen during pregnancy. The areola is typically circular and can vary in size from 25 to 100 mm in diameter. The areolar region is characterized by small, raised areolar glands that secrete lubricating fluid during lactation to protect the nipple from chafing. When a baby nurses, or draws milk from the breast, the entire areolar region is taken into the mouth.

Breast milk is produced by the mammary glands , which are modified sweat glands. The milk itself exits the breast through the nipple via 15 to 20 lactiferous ducts that open on the surface of the nipple. These lactiferous ducts each extend to a lactiferous sinus that connects to a glandular lobe within the breast itself that contains groups of milk-secreting cells in clusters called alveoli (see Figure \(\PageIndex{9}\)). The clusters can change in size depending on the amount of milk in the alveolar lumen. Once milk is made in the alveoli, stimulated myoepithelial cells that surround the alveoli contract to push the milk to the lactiferous sinuses. From here, the baby can draw milk through the lactiferous ducts by suckling. The lobes themselves are surrounded by fat tissue, which determines the size of the breast; breast size differs between individuals and does not affect the amount of milk produced. Supporting the breasts are multiple bands of connective tissue called suspensory ligaments that connect the breast tissue to the dermis of the overlying skin.

Hormonal Birth Control

Aging and the Female Reproductive System

Chapter Review

Essay Questions

Q. Read from the chapter about the ovulation and its initiation in response to the release of FSH and LH from the pituitary gland. What specialized structures help guide the oocyte from the ovary into the uterine tube?

A. The fimbriae sweep the oocyte into the uterine tube.

Q. Watch this series of videos to look at the movement of the oocyte through the ovary. The cilia in the uterine tube promote movement of the oocyte. What would likely occur if the cilia were paralyzed at the time of ovulation?

A. The oocyte may not enter the tube and may enter the pelvic cavity.

Review Questions

Q. What are the female gonads called?

C. oviducts

Q. When do the oogonia undergo mitosis?

A. before birth

B. at puberty

C. at the beginning of each menstrual cycle

D. during fertilization

Q. From what structure does the corpus luteum originate?

A. uterine corpus

B. dominant follicle

C. fallopian tube

D. corpus albicans

Q. Where does fertilization of the egg by the sperm typically occur?

C. uterine tube

Q. Why do estrogen levels fall after menopause?

A. The ovaries degrade.

B. There are no follicles left to produce estrogen.

C. The pituitary secretes a menopause-specific hormone.

D. The cells of the endometrium degenerate.

Q. The vulva includes the ? .

A. lactiferous duct, rugae, and hymen

B. lactiferous duct, endometrium, and bulbourethral glands

C. mons pubis, endometrium, and hymen

D. mons pubis, labia majora, and Bartholin’s glands

Critical Thinking Questions

Q. Follow the path of ejaculated sperm from the vagina to the oocyte. Include all structures of the female reproductive tract that the sperm must swim through to reach the egg.

A. The sperm must swim upward in the vagina, through the cervix, and then through the body of the uterus to one or the other of the two uterine tubes. Fertilization generally occurs in the uterine tube.

Q. Identify some differences between meiosis in men and women.

A. Meiosis in the man results in four viable haploid sperm, whereas meiosis in the woman results in a secondary oocyte and, upon completion following fertilization by a sperm, one viable haploid ovum with abundant cytoplasm and up to three polar bodies with little cytoplasm that are destined to die.

Q. Explain the hormonal regulation of the phases of the menstrual cycle.

A. As a result of the degradation of the corpus luteum, a decline in progesterone concentrations triggers the shedding of the endometrial lining, marking the menses phase of the menstrual cycle. Low progesterone levels also reduce the negative feedback that had been occurring at the hypothalamus and pituitary, and result in the release of GnRH and, subsequently, FSH and LH. FSH stimulates tertiary follicles to grow and granulosa and theca cells begin to produce increased amounts of estrogen. High estrogen concentrations stimulate the endometrial lining to rebuild, marking the proliferative phase of the menstrual cycle. The high estrogen concentrations will eventually lead to a decrease in FSH because of negative feedback, resulting in atresia of all but one of the developing tertiary follicles. The switch to positive feedback that occurs with elevated estrogen production from the dominant follicle stimulates the LH surge that will trigger ovulation. The luteinization of the granulosa cells of the collapsed follicle forms the progesterone-producing corpus luteum. Progesterone from the corpus luteum causes the endometrium to prepare for implantation, in part by secreting nutrient-rich fluid. This marks the secretory phase of the menstrual cycle. Finally, in a non-fertile cycle, the corpus luteum will degrade and menses will occur.

Q. Endometriosis is a disorder in which endometrial cells implant and proliferate outside of the uterus—in the uterine tubes, on the ovaries, or even in the pelvic cavity. Offer a theory as to why endometriosis increases a woman’s risk of infertility.

A. Endometrial tissue proliferating outside of the endometrium—for example, in the uterine tubes, on the ovaries, or within the pelvic cavity—could block the passage of sperm, ovulated oocytes, or a zygote, thus reducing fertility.

Contributors and Attributions

OpenStax Anatomy & Physiology (CC BY 4.0). Access for free at https://openstax.org/books/anatomy-and-physiology

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5 min read. The female reproductive system is designed to carry out several functions. It produces the female egg cells necessary for reproduction, called the ova or oocytes. The system is ...
Female Reproductive System Anatomy and Physiology
Uterus. The uterus is described as a hollow, muscular, pear-shaped organ. It is located at the lower pelvis, which is posterior to the bladder and anterior to the rectum. The uterus has an estimated length of 5 to 7 cm and width of 5 cm. it is 2.5 cm deep in its widest part. For non-pregnant women, it is approximately 60g in weight.
Reproductive system and pregnancy
Placenta accreta. UTIs in pregnancy. Blood conditions in pregnancy. Sheehan syndrome. Postpartum hemorrhage. Uterine inversion. Diabetes in pregnancy. Preterm labor. C-section.
Female reproductive system
14. Uterus Pear-shaped muscular organ in the female reproductive tract. The fundus is the upper portion of the uterus where pregnancy occurs. The cervix is the lower portion of the uterus that connects with the vagina and serves as a sphincter to keep the uterus closed during pregnancy until it is time to deliver a baby. The uterus expands considerably during the reproductive process. The ...
Welcome to the reproductive system (video)
Transcript. Humans reproduce and bear offspring through the reproductive system, which includes pregnancy, fetal development, and birth. Males have testes that produce sperm and a penis for delivery. Females have ovaries that produce eggs, a uterus for baby development, and breasts for milk production. Hormones regulate these organs.
26.1A: Overview of the Male and Female Reproductive Systems
The male reproductive system consists of external organs. The testes in the scrotum produce the male gamete, sperm, which is ejaculated in seminal fluid by the penis. The female reproductive system primarily consists of internal organs. The female gamete, ovum, is produced in the ovaries and is released monthly to travel to the uterus via the ...
Physiology, Female Reproduction
The reproductive system in females is responsible for producing gametes (called eggs or ova), certain sex hormones, and maintaining fertilized eggs as they develop into mature fetuses and become ready for delivery. A female's reproductive years are between menarche (the first menstrual cycle) and menopause (cessation of menses for 12 consecutive months). During this period, cyclical ...
Human reproductive system
zygote. gonad. gamete. male reproductive system. female reproductive system. human reproductive system, organ system by which humans reproduce and bear live offspring. Provided all organs are present, normally constructed, and functioning properly, the essential features of human reproduction are (1) liberation of an ovum, or egg, at a specific ...
17 Female Reproductive System
The female reproductive system is located primarily inside the pelvic cavity. The female gonads are called ovaries and the gamete they produce is called an oocyte. Figure 17.1 Female Reproductive System. The major organs of the female reproductive system are located inside the pelvic cavity. From Betts et al., 2013.
Anatomy and Physiology of the Female Reproductive System
The female reproductive system functions to produce gametes and reproductive hormones, just like the male reproductive system; however, it also has the additional task of supporting the developing fetus and delivering it to the outside world. Unlike its male counterpart, the female reproductive system is located primarily inside the pelvic cavity.
22.5: Laboratory Activities and Assignment
Part 3: Reproductive Systems Laboratory Activities "Human Anatomy Lab Manual" by Malgosia Wilk-Blaszczak , Mavs Open Press , University of Texas at Arlington is licensed under CC BY 4.0 This page titled 22.5: Laboratory Activities and Assignment is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Rosanna ...
Male and female reproductive system assignment
Male and female reproductive system assignment. anatomy and physiology assignment on male and female reproductive systems. Course. Human Anat. And Physiol. II (BIOL 2110) 22 Documents. Students shared 22 documents in this course. University Auburn University at Montgomery. Academic year: 2021/2022.
19.3: Anatomy and Physiology of the Female Reproductive System
Vagina. The vagina, shown at the bottom of Figure 19.3.1 19.3. 1 and Figure 19.3.1 19.3. 1, is a muscular canal (approximately 10 cm long) that serves as the entrance to the reproductive tract. It also serves as the exit from the uterus during menses and childbirth.