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Biology LibreTexts

22.2: Introduction to the Reproductive System

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  • Page ID 17787

  • Suzanne Wakim & Mandeep Grewal
  • Butte College

It’s All About Sex

A tiny sperm breaks through the surface of a huge egg. Voilà! In nine months, a new baby will be born. Like most other multicellular organisms, human beings reproduce sexually. In human sexual reproduction, individuals with testes produce sperm, and individuals with ovaries produce eggs, and a new offspring forms when a sperm unites with an egg. How do sperm and eggs form? And how do they arrive together at the right place and time so they can unite to form a new offspring? These are functions of the reproductive system.

sperm and egg fertilization

What Is the Reproductive System?

The reproductive system is the human organ system responsible for the production and fertilization of gametes (sperm or eggs) and carrying of a fetus. Both both sexes gonads produce gametes. A gamete is a haploid cell that combines with another haploid gamete during fertilization, forming a single diploid cell called a zygote. Besides producing gametes, the gonads also produce sex hormones. Sex hormones are endocrine hormones that control the development of sex organs before birth, sexual maturation at puberty, and reproduction once sexual maturation has occurred. Other reproductive system organs have various functions, such as maturing gametes, delivering gametes to the site of fertilization, and providing an environment for the development and growth of offspring.

Sex Differences in the Reproductive System

The reproductive system is the only human organ system that is significantly different between males and females. Embryonic structures that will develop into the reproductive system start out the same in males and females, but by birth, the reproductive systems have differentiated. How does this happen?

Sex Differentiation

Starting around the seventh week after conception in genetically male (XY) embryos, a gene called SRY on the Y chromosome (Figure \(\PageIndex{2}\)) initiates the production of multiple proteins. These proteins cause undifferentiated gonadal tissue to develop into testes. Testes secrete hormones — including testosterone — that trigger other changes in the developing offspring (now called a fetus), causing it to develop a complete male reproductive system. Without a Y chromosome, an embryo will develop ovaries, that will produce estrogen. Estrogen, in turn, will lead to the formation of the other organs of a female reproductive system.

Human Y chromosome

Homologous Structures

Undifferentiated embryonic tissues develop into different structures in male and female fetuses. Structures that arise from the same tissues in males and females are called homologous structures . The testes and ovaries, for example, are homologous structures that develop from the undifferentiated gonads of the embryo. Likewise, the penis and clitoris are homologous structures that develop from the same embryonic tissues.

Sex Hormones and Maturation

Male and female reproductive systems are different at birth, but they are immature and incapable of producing gametes or sex hormones. Maturation of the reproductive system occurs during puberty when hormones from the hypothalamus and pituitary gland stimulate the testes or ovaries to start producing sex hormones again. The main sex hormones are testosterone and estrogen . Sex hormones, in turn, lead to the growth and maturation of the reproductive organs, rapid body growth, and the development of secondary sex characteristics , such as body and facial hair and breasts.

Role of Sex Hormones in Transgender Treatment

Feminizing or masculinizing hormone therapy is the administration of exogenous endocrine agents to induce changes in physical appearance. Since hormone therapy is inexpensive relative to surgery and highly effective in the development of secondary sex characteristics (e.g., facial and body hair in female-to-male [FTM] individuals or breast tissue in male-to-females [MTFs]), hormone therapy is often the first, and sometimes only, medical gender affirmation intervention accessed by transgender individuals looking to develop masculine or feminine characteristics consistent with their gender identity. In some cases, hormone therapy may be required before surgical interventions can be conducted. Trans-females are prescribed estrogen and anti-testosterone medication, such as cyproterone acetate and spironolactone. Trans-men are prescribed testosterone.

Male Reproductive System

The main structures of the male reproductive system are external to the body and illustrated in Figure \(\PageIndex{3}\). The two testes (singular, testis) hang between the thighs in a sac of skin called the scrotum. The testes produce both sperm and testosterone. Resting atop each testis is a coiled structure called the epididymis (plural, epididymes). The function of the epididymes is to mature and store sperm. The penis is a tubular organ that contains the urethra and has the ability to stiffen during sexual arousal. Sperm passes out of the body through the urethra during a sexual climax (orgasm). This release of sperm is called ejaculation.

In addition to these organs, there are several ducts and glands that are internal to the body. The ducts, which include the vas deferens (also called the ductus deferens), transport sperm from the epididymis to the urethra. The glands, which include the prostate gland and seminal vesicles, produce fluids that become part of semen. Semen is the fluid that carries sperm through the urethra and out of the body. It contains substances that control pH and provide sperm with nutrients for energy.

Male reproductive system

Female Reproductive System

female reproductive system

The main structures of the female reproductive system are internal to the body and shown in Figure \(\PageIndex{4}\). They include the paired ovaries, which are small, oval structures that produce eggs and secrete estrogen. The two Fallopian tubes (aka uterine tubes) start near the ovaries and end at the uterus. Their function is to transport eggs from the ovaries to the uterus. If an egg is fertilized, it usually occurs while it is traveling through a Fallopian tube. The uterus is a pear-shaped muscular organ that functions to carry a fetus until birth. It can expand greatly to accommodate a growing fetus, and its muscular walls can contract forcefully during labor to push the baby into the vagina. The vagina is a tubular tract connecting the uterus to the outside of the body. The vagina is where sperm are usually deposited during sexual intercourse and ejaculation. The vagina is also called the birth canal because a baby travels through the vagina to leave the body during birth.

The external structures of the female reproductive system are referred to collectively as the vulva. They include the clitoris, which is homologous to the male penis. They also include two pairs of labia (singular, labium), which surround and protect the openings of the urethra and vagina.

  • What is the reproductive system?
  • Define gonad.
  • What are sex hormones? What are their general functions?
  • Distinguish between male and female sex hormones.
  • How does the differentiation of the reproductive system occur in males and females?
  • In the context of the human male and female reproductive systems, what are homologous structures?
  • When and how does the human reproductive system mature?
  • List the organs of the male reproductive system.
  • List the organs of the female reproductive system.
  • What are female gametes called? What are male gametes called?
  • True or False: The vagina is the homologous structure to the penis.
  • rue or False: In the absence of a Y chromosome in humans, ovaries will develop.
  • Fallopian tubes
  • all of the above
  • Fallopian tube
  • Explain the difference between the vulva and the vagina.

Explore More

People's sense of gender identity does not always match their anatomy. Some people do not identify as either male or female, and instead, they identify as non-binary, or genderqueer. Others may identify as a gender that is the opposite of what is typically associated with their chromosomes or reproductive organs. These people are called transgender, and they may choose to transition to the opposite gender, a process that may or may not involve physical modifications. Watch the video below to learn about the use of hormones in gender transitioning.

Sex determination may be more complicated than originally thought. Check out this video to learn more:

Attributions

  • Sperm-Egg ; public domain via Wikimedia Commons
  • Human Y chromosome by National Center for Biotechnology Information ( NCBI ); public domain via Wikimedia Commons
  • Male Reproductive System by Charles Molnar and Jane Gair; CC BY 4.0 from Concepts of Biology - 1st Canadian edition
  • Female Reproductive System by Blausen.com staff (2014). " Medical gallery of Blausen Medical 2014 ". WikiJournal of Medicine 1 (2). DOI : 10.15347/wjm/2014.010 . ISSN 2002-4436 . licensed CC BY 3.0 via Wikimedia Commons
  • Text adapted from Human Biology by CK-12 licensed CC BY-NC 3.0
  • Some text is adapted from White Hughto JM, Reisner SL.. A systematic review of the effects of hormone therapy on psychological functioning and quality of life in transgender individuals . Transgend Health. 2016;1(1):21-31 CC BY 4.0

27.2 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 ( Figure 27.9 ). 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 27.10 ). 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).

The vagina , shown at the bottom of Figure 27.9 and Figure 27.10 , 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 (see Figure 27.9 ). 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 ( Figure 27.11 ). 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 27.11 , 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.

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 Connection

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 ( Figure 27.12 ). 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 27.12 )—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.

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 ( Figure 27.13 ). 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.

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 27.13 ). 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” (see Figure 27.12 ). 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 ( Figure 27.14 ). 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.

Interactive Link

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.

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 (see Figure 27.14 ). 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 27.15 , 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.

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 27.15 ). 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 (see Figure 27.15 ). 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 ( Figure 27.16 ). 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.

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 ( Figure 27.17 ), 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 27.17 ). 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.

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 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.

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Theme 5: How Do We Control Our Fertility?

5.1 Human Reproductive Anatomy

Human reproductive anatomy.

In general, the reproductive structures in humans can be divided into three main categories:  gonads,  internal genitalia and external genitalia.  The gonads are the organs in which gametes , the cells that fuse in fertilization to form new individuals, develop and mature.  All other reproductive structures are called genitalia, or genitals.  Internal genitalia are found inside of the body, while external genitalia are visible from the outside.  The structures seen in adult males and females actually come from the same precursors in embryos, so there are many similarities in both structure and function between males and females. There is also a wide spectrum of structures present in any one individual; many people have structures that resemble a combination of male and female structures, or that resemble neither. In this textbook, we will define “male” and “female” based on individuals who have the most typical structures characteristic of those two sexes; other types of structures are also normal and common. We will describe the functions of these structures during vaginal sexual intercourse, since that is the sexual act used in reproduction; keep in mind that other types of sexual activity are also common and normal.

Male Reproductive Anatomy

In the male reproductive system, the  scrotum  houses the testicles or testes (singular: testis), including providing passage for blood vessels, nerves, and muscles related to testicular function. The  testes are gonads, and they produce sperm (the male gametes) and some reproductive hormones. Each testis is approximately 2.5 by 3.8 cm (1.5 by 1 in) in size and divided into wedge-shaped lobules by connective tissue called septa.

Sperm are immobile at body temperature; therefore, the scrotum and penis are external to the body, as illustrated in  Figure 1 so that a proper temperature is maintained for motility.

Illustration shows a cross section of the penis and testes. The penis widens at the end, into the glans, which is surrounded by the foreskin. The urethra is an opening that runs through the middle of the penis to the bladder. The tissue surrounding the urethra is the Corpus spongiosum, and above the Corpus spongiosum is the Corpus cavernosum. The testes, located immediately behind the penis, are covered by the scrotum. Seminiferous tubules are located in the testes. The epididymis partly surrounds the sac containing the seminiferous tubules. The Vas deferens is a tube connecting the seminiferous tubules to the ejaculatory duct, which begins in the prostate gland. The prostate gland is located behind and below the bladder. The seminal vesicle, located above the prostate, also connects to the seminal vesicle. The bulbourethral gland connects to the ejaculatory duct where the ejaculatory duct enters the penis.

The internal genitalia in males are important for the production of sperm, and of other components of . the semen. Sperm mature in seminiferous tubules  that are coiled inside the testes, as illustrated in  Figure 1 . The walls of the seminiferous tubules are made up of the developing sperm cells, with the least developed sperm at the periphery of the tubule and the fully developed sperm in the lumen. The sperm cells are mixed with “nursemaid” cells called Sertoli cells which protect the germ cells and promote their development. Other cells mixed in the wall of the tubules are the interstitial cells of Leydig . These cells produce high levels of testosterone once the male reaches adolescence.

When the sperm have developed flagella and are nearly mature, they leave the testicles and enter the epididymis, shown in  Figure 1 . This structure resembles a comma and lies along the top and posterior portion of the testes; it is the site of sperm maturation. The sperm leave the epididymis and enter the vas deferens (or ductus deferens), which carries the sperm, behind the bladder, and forms the ejaculatory duct with the duct from the seminal vesicles. During a vasectomy, a section of the vas deferens is removed, preventing sperm from being passed out of the body during ejaculation and preventing fertilization.

Semen  is a mixture of sperm and spermatic duct secretions (about 10 percent of the total) and fluids from accessory glands that contribute most of the semen’s volume. Sperm are haploid cells, consisting of a flagellum as a tail, a neck that contains the cell’s energy-producing mitochondria, and a head that contains the genetic material.  Figure 2 shows a micrograph of human sperm as well as a diagram of the parts of the sperm. An acrosome is found at the top of the head of the sperm. This structure contains enzymes that can digest the protective coverings that surround the egg to help the sperm penetrate and fertilize the egg. An ejaculate (a single emission of sperm) will contain from two to five milliliters of fluid with from 50–120 million sperm per milliliter.

assignment for reproductive system

The bulk of the semen comes from the accessory glands associated with the male reproductive system. These are the seminal vesicles, the prostate gland, and the bulbourethral gland, all of which are illustrated in  Figure 1 . The  seminal vesicles  are a pair of glands that lie along the posterior border of the urinary bladder. The glands make a solution that is thick, yellowish, and alkaline. As sperm are only motile in an alkaline environment, a basic pH is important to reverse the acidity of the vaginal environment. The solution also contains mucus, fructose (a sperm mitochondrial nutrient), a coagulating enzyme, ascorbic acid, and local-acting hormones called prostaglandins. The seminal vesicle glands account for 60 percent of the bulk of semen.

The  penis , illustrated in  Figure 1 , is an organ that drains urine from the renal bladder and functions as a copulatory organ during intercourse. The penis contains three tubes of erectile tissue running through the length of the organ. These consist of a pair of tubes on the dorsal side, called the corpus cavernosum, and a single tube of tissue on the ventral side, called the corpus spongiosum. This tissue will become engorged with blood, becoming erect and hard, in preparation for sexual intercourse. The organ is inserted into the vagina culminating with an ejaculation. During intercourse, the smooth muscle sphincters at the opening to the renal bladder close and prevent urine from entering the penis. An orgasm is a two-stage process: first, glands and accessory organs connected to the testes contract, then semen (containing sperm) is expelled through the urethra during ejaculation. After intercourse, the blood drains from the erectile tissue and the penis becomes flaccid.

The walnut-shaped  prostate gland  surrounds the urethra, the connection to the urinary bladder. It has a series of short ducts that directly connect to the urethra. The gland is a mixture of smooth muscle and glandular tissue. The muscle provides much of the force needed for ejaculation to occur. The glandular tissue makes a thin, milky fluid that contains citrate (a nutrient), enzymes, and prostate specific antigen (PSA). PSA is a proteolytic enzyme that helps to liquefy the ejaculate several minutes after release from the male. Prostate gland secretions account for about 30 percent of the bulk of semen.

The  bulbourethral gland , or Cowper’s gland, releases its secretion prior to the release of the bulk of the semen. It neutralizes any acid residue in the urethra left over from urine. This usually accounts for a couple of drops of fluid in the total ejaculate and may contain a few sperm. Withdrawal of the penis from the vagina before ejaculation to prevent pregnancy may not work if sperm are present in the bulbourethral gland secretions. The location and functions of the male reproductive organs are summarized in  Table 1 .

Female Reproductive Anatomy

A number of reproductive structures are exterior to the female’s body. These include the breasts and the vulva, which consists of the mons pubis, clitoris, labia majora, labia minora, and the vestibular glands, all illustrated in  Figure 3 . The location and functions of the female reproductive organs are summarized in  Table 2 . The mons pubis is a round, fatty area that overlies the pubic bone. The clitoris  is a structure with erectile tissue that contains a large number of sensory nerves and serves as a source of stimulation during intercourse. The  labia majora  are a pair of elongated folds of tissue that run posterior from the mons pubis and enclose the other components of the vulva. The labia majora derive from the same tissue that produces the scrotum in a male. The  labia minora  are thin folds of tissue centrally located within the labia majora. These labia protect the openings to the vagina and urethra. The mons pubis and the anterior portion of the labia majora become covered with hair during adolescence; the labia minora is hairless. The greater vestibular glands are found at the sides of the vaginal opening and provide lubrication during intercourse. The vulva is the name for the entire set of external genitalia in the inguinal (groin) area of females; in common language this is sometimes referred to as the vagina, but that is not anatomically accurate; the vagina is an entirely internal structure.

Side and front views of female reproductive organs are shown. The vagina is wide at the bottom, and narrows into the cervix. Above the cervix is the uterus, which is shaped like a triangle pointing down. Fallopian tubes extend from the top sides of the uterus. The Fallopian tubes curve back in toward the uterus, and end in fingerlike appendages called fimbriae. The ovaries are located between the fimbriae and the uterus. The urethra is located in front of the vagina, and the rectum is located behind. The clitoris is a structure located in front of the urethra. The labia minora and labia majora are folds of tissue on either side of the vagina.

The breasts consist of mammary glands and fat. The size of the breast is determined by the amount of fat deposited behind the gland. Each gland consists of 15 to 25 lobes that have ducts that empty at the nipple and that supply the nursing child with nutrient- and antibody-rich milk to aid development and protect the child.

Internal female reproductive structures include ovaries, oviducts, the  uterus , and the vagina, shown in  Figure 3 . The two ovaries (the female gonads) are held in place in the abdominal cavity by a system of ligaments. Ovaries consist of a medulla and cortex: the medulla contains nerves and blood vessels to supply the cortex with nutrients and remove waste. The outer layers of cells of the cortex are the functional parts of the ovaries. The cortex is made up of follicular cells that surround eggs that develop during fetal development in utero . During the menstrual period, a batch of follicular cells develops and prepares the eggs for release. At ovulation, one follicle ruptures and one egg is released, as illustrated in  Figure 4a .

Illustration A shows a cross section of a human ovary, which is oval with a stem-like structure at one end that anchors it to the uterus. The central part of the ovary is the medulla, and the outer part is the cortex. Follicles exist in the cortex. Small, immature follicles are located near this stem-like structure. As a follicle matures, it grows and moves toward the edge of the ovary opposite the stem, it ruptures, releasing the egg. The follicle is now called a corpus luteum. The corpus luteum matures and moves back toward the stem, along the opposite edge of the ovary from which the follicle matured. The corpus luteum shrinks and eventually disintegrates. The light micrograph shows an oval follicle with a large oocyte located at the center. Around the oocyte are much smaller cells.

The  oviducts , or fallopian tubes, extend from the uterus in the lower abdominal cavity to the ovaries, but they are not in contact with the ovaries. The lateral ends of the oviducts flare out into a trumpet-like structure and have a fringe of finger-like projections called fimbriae, illustrated in  Figure 4b . When an egg is released at ovulation, the fimbrae help the non-motile egg enter into the tube and passage to the uterus. The walls of the oviducts are ciliated and are made up mostly of smooth muscle. The cilia beat toward the middle, and the smooth muscle contracts in the same direction, moving the egg toward the uterus. Fertilization usually takes place within the oviducts and the developing embryo is moved toward the uterus for development. It usually takes the egg or embryo a week to travel through the oviduct. Sterilization in females is called a tubal ligation; it is analogous to a vasectomy in males in that the oviducts are severed and sealed.

The uterus is a structure about the size of a females’s fist. This is lined with an endometrium rich in blood vessels and mucus glands. The uterus supports the developing embryo and fetus during gestation. The thickest portion of the wall of the uterus is made of smooth muscle. Contractions of the smooth muscle in the uterus aid in passing the baby through the vagina during labor. A portion of the lining of the uterus sloughs off during each menstrual period, and then builds up again in preparation for an implantation. Part of the uterus, called the cervix, protrudes into the top of the vagina. A small opening called the cervical orifice allows menstrual fluid out of the cervix into the vagina, and sperm into the uterus.  During childbirth the cervical orifice is greatly enlarged.

The  vagina is a muscular tube that serves several purposes. It allows menstrual flow to leave the body. It is the receptacle for the penis during intercourse and the vessel for the delivery of offspring. It is lined cells that produce acidic secretions that limit the growth of microbes that could potentially travel into the uterus.

Development of Reproductive Organs in Humans.

The reproductive tissues of male and female humans develop similarly  in utero (in a fetus developing in the mother’s uterus) for the first several weeks of gestation.  The hormone testosterone is typically only released in embryos that have a male sex chromosome (the Y chromosome, discussed in the next chapter), and this hormone controls the generation of reproductive structures. A low level of the hormone testosterone is released from male gonads in the developing embryos, starting at around the second month of gestation. Testosterone causes the undeveloped tissues to differentiate into male sexual organs. When testosterone is absent, the tissues develop into female sexual tissues. Primitive gonads become testes or ovaries. Tissues that produce a penis in males produce a clitoris in females. The tissue that will become the scrotum in a male becomes the labia in a female; that is, they are homologous structures.  Because of this, there are often variations in development resulting in structures that may have characteristics of both sexes, or of neither sex, depending on hormonal levels and other factors present during embryogenesis.  These variations in sexual structures are quite common and normal.

Sexual Response During Intercourse

The sexual response in humans is both psychological and physiological. Both sexes experience sexual arousal through psychological and physical stimulation. There are four phases of the sexual response. During phase one, called excitement, vasodilation leads to vasocongestion in erectile tissues in both males and females. The nipples, clitoris, labia, and penis engorge with blood and become enlarged. Vaginal secretions are released to lubricate the vagina to facilitate intercourse. During the second phase, called the plateau, stimulation continues, the outer third of the vaginal wall enlarges with blood, and breathing and heart rate increase.

During phase three, or orgasm, rhythmic, involuntary contractions of muscles occur in both sexes. In the male, the reproductive accessory glands and tubules constrict placing semen in the urethra, then the urethra contracts expelling the semen through the penis. In females, the uterus and vaginal muscles contract in waves that may last slightly less than a second each. During phase four, or resolution, the processes described in the first three phases reverse themselves and return to their normal state. Males experience a refractory period in which they cannot maintain an erection or ejaculate for a period of time ranging from minutes to hours.

Section Summary

The reproductive structures that evolved in humans allow males and females to mate, fertilize internally, and support the growth and development of offspring. Reproductive structures include gonads, internal and external genitalia. Some male and female reproductive structures have analogous functions and are derived from common precursor structures. Both males and females have four stages of the sexual response.

Human Biology Copyright © by Sarah Malmquist and Kristina Prescott is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

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23.1: Introduction to the Reproductive System

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Chapter Learning Objectives:

  • Describe the anatomy of the male and female reproductive systems, including their accessory structures
  • Explain the role of hypothalamic and pituitary hormones in male and female reproductive function
  • Trace the path of a sperm cell from its initial production through fertilization of an oocyte
  • Explain the events in the ovary prior to ovulation
  • Describe the development and maturation of the sex organs and the emergence of secondary sex characteristics during puberty

Small, uncoordinated, and slick with amniotic fluid, a newborn encounters the world outside of her mother’s womb. We do not often consider that a child’s birth is proof of the healthy functioning of both her mother’s and father’s reproductive systems. Moreover, her parents’ endocrine systems had to secrete the appropriate regulating hormones to induce the production and release of unique male and female gametes, reproductive cells containing the parents’ genetic material (one set of 23 chromosomes). Her parent’s reproductive behavior had to facilitate the transfer of male gametes—the sperm—to the female reproductive tract at just the right time to encounter the female gamete, an oocyte (egg). Finally, combination of the gametes (fertilization) had to occur, followed by implantation and development. In this chapter, you will explore the male and female reproductive systems, whose healthy functioning can culminate in the powerful sound of a newborn’s first cry.

Color photo of bulging follicle on ovary surface, about to rupture, which is ovulation.

Brief Overview

Before diving into the details, let's cover some basic common terms. Unique for its role in human reproduction, a gamete is a specialized sex cell carrying 23 chromosomes—one half the number in body cells. Gonads are the organs that make the gametes. Once the gametes are made, they travel in tubular structures. These structures are often the site for permanent sterilization procedures because if the gametes of the opposite sex cannot meet, then fertilization will not be possible. (Table 23.1.1) Comparing the midsagittal view of the female and male pelvis, we see multiple differences (Figure 23.1.2). Discussions on the female reproductive anatomy will be covered in section 23.3. Discussions on the male reproductive anatomy will be covered in section 23.2.

Table 23.1.1 Male and Female Reproductive Systems

Drawings of the sagittal views of female pelvis in (a) and male pelvis in (b) with reproductive, urinary, and digestive structures.

Contributors and Attributions

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

  • Biology Article

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.

Table of Contents:

Labelled diagram of female reproductive system.

  • Female Reproductive System Anatomy

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.

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The vagina is a muscular and elastic tube that connects the cervix to the external body. It functions as the receptacle for the penis in sexual intercourse and delivers sperm to the fallopian tubes and uterus. It also acts as a birth canal by expanding to allow delivery of the fetus during childbirth.

The external genitalia comprises the labia minora , labia majora and clitoris

Ovulation is the process of releasing the eggs from the ovaries. This process takes place as soon as the follicle is fully grown and reaches its size along with the accumulation of liquid in the follicle without a significant rise in pressure. As the follicle swells out, a small oval-shaped area, the stigma or macula pellucida appears sticking outward as a clear cone area and later undergoes localized changes in colour, integrity, and translucency. The secretion of estrogen hormones reaches the maximum level before the ovulation. After the surge of luteinizing hormone, ovulation occurs at the site of the stigma. This surge is essential for ovulation. Ovulation is the process in which the follicle is separated by releasing of follicular fluid along with the ovum surrounded by the corona radiata. The cells of the corona radiata will separate later in the presence of spermatozoa. In ruminants, the oocytes have already lost their corona at the time of ovulation. The very active fimbriae, end of the oviduct picks up the ovum. If fertilized ovum or zygote undergoes cleavage and makes its way to the uterus for implantation. If not fertilized, it degenerates within 24 hours.

All females, after reaching their puberty produce mature egg cell every month during a process called the menstrual cycle .  During this period, an ovary discharges a mature egg, which travels to the uterus. In the uterus, if the egg is not fertilized, the lining in the uterine sheds away and a new cycle begins. Overall a menstrual cycle lasts for 28 days, in some cases, these cycles may either last for 21 days or as long as 35 days in some individuals. The entire process of the menstrual cycle is controlled by the endocrine system and the hormones involved are FSH, LH, estrogen, and progesterone. Both FSH and LH hormones are produced by the pituitary gland,  whereas estrogen and progesterone hormones are produced by the ovaries. Alon with the hormonal disorders, there are many other factors, which are responsible for the disturbance in the menstrual cycle. The responsible factors include diet, exercise, stress and weight gain or loss affects the menstrual cycle. The cycle may be irregular at times, especially during puberty.  The menstrual cycles occur every month from the time of puberty up to the age of 45 to 55, except during pregnancy. After the age of 55 ovaries slows down their production of hormone and release of mature eggs. Progressively, the menstrual cycle stops, therefore, the woman is no longer able to become pregnant.

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.

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Further Reading

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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Biology Assignment: Human Reproductive System Assignment

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Abortions outside medical system increased sharply after Roe fell, study finds

Researchers report that volunteer-led networks distributing abortion pills helped drive a rise in ‘self-managed’ abortions.

The number of women using abortion pills to end their pregnancies on their own without the direct involvement of a U.S.-based medical provider rose sharply in the months after the Supreme Court eliminated a constitutional right to abortion, according to the most comprehensive examination to date of how many people have ended their pregnancies outside of the formal medical system since the ruling.

Nearly 28,000 additional doses of pills intended for “self-managed” abortions were provided in the six months after the fall of Roe v. Wade — more than quadrupling the average number of abortion pills provided that way per month before the decision and suggesting that many women have turned to medication abortion to circumvent state bans.

The research — published in JAMA on Monday , the day before the highly anticipated Supreme Court arguments on a challenge to a key abortion drug — highlights the importance of abortion pills in post- Roe America. Before the ruling legalized abortion nationwide in 1973, women seeking abortions were forced to find someone to perform an illegal surgical procedure, leading to thousands of deaths . Today, the process for accessing abortion is far easier and safer, with a rapidly expanding online and community-based network of pill suppliers sending pills through the mail into states with strict bans.

Other studies have estimated that approximately 32,000 fewer abortions occurred at licensed brick-and-mortar and telehealth clinics in the six months following the fall of Roe . But the jump in self-managed abortions offsets nearly that whole figure.

assignment for reproductive system

Supply of abortion pills for

self-managed abortions

The supply of abortion pills outside of the formal health-care setting increased sharply in the six months after Dobbs v. Jackson Women’s Health Organization , a landmark ruling that eliminated the constitutional right to abortion. A major factor in the increase was the rise of community-based, volunteer-led networks that organized to help women in states with abortion bans.

Online vendors

Telemedicine

Community networks

Source: Provision of Medications for Self-managed Abortion

Before and After the Dobbs v Jackson Women’s Health

Organization decision. JAMA (2024)

assignment for reproductive system

Source: Provision of Medications for Self-managed Abortion Before and After

the Dobbs v Jackson Women’s Health Organization decision. JAMA (2024)

assignment for reproductive system

Supply of abortion pills for self-managed abortions

“The numbers we’re looking at seem to suggest that [self-managed abortion] is more mainstream than perhaps we thought,” said Abigail Aiken, a professor at the University of Texas at Austin and the lead author of the study. “This is something people are doing on a larger scale.”

Women in states with bans are also using the traditional health-care system to access abortion, traveling out of state to pick up pills or to have a procedure at a clinic in a state where abortion remains legal. A different study published last week by the Guttmacher Institute, which supports abortion rights, revealed that the overall number of abortions facilitated within the formal health-care system increased last year despite the bans, with medication abortions accounting for 63 percent of the more than 1 million abortions performed in 2023.

Taken together, the flurry of new data points to a perhaps surprising result of the fall of Roe : While the ruling has made abortion more difficult to access for people in antiabortion states, a large portion of those women have been able to navigate around the laws and end their pregnancies.

Self-managed abortions with pills are facilitated in a legal gray area. Women obtaining abortions by mail are not breaking the law themselves; abortion bans are designed to penalize only doctors and others involved in facilitating an abortion. Those involved with distributing the pills could potentially be charged. In many states, abortion bans carry penalties of at least several years in prison.

The landscape of self-managed abortion is sprawling and difficult to quantify, Aiken said. According to Plan C, an abortion rights organization that tests pills and publishes a list of verified sources online, at least 25 websites now mail abortion medication into states that ban the procedure, along with several telehealth clinics and community-based networks.

Aiken identified 15 distinct sources for abortion pills that were operating outside of the formal health-care setting in the first six months after Roe fell, most of which shared with the researchers month-by-month data on the number of pills they distributed to U.S. patients during that period. Some sources relayed the numbers without providing internal documentation, Aiken said, because they do not keep formal records.

Rebecca Gomperts, the founder of Aid Access, the largest telehealth clinic mailing pills into states with abortion bans, and Elisa Wells, a founder of Plan C, are co-authors of the study.

The various sources that mail pills for self-managed abortions operate with very different models, offering a range of medical and emotional support through the process of passing a pregnancy at home, according to the new study.

In the first six months after the Supreme Court decision, the JAMA study shows that most women who chose to self-manage their abortions obtained pills through networks of volunteers that quickly mobilized and expanded after the ruling. These networks — one of the largest of which is based in Mexico — buy pills from international pharmacies, then mail them to people for free without a prescription, offering peer support but typically no direct access to a doctor. The pills often arrive unsealed, according to Plan C.

Along with community-based networks, people are also obtaining pills through internationally based telehealth clinics, which provide a prescription from a doctor, or other websites that sell pills typically without offering any kind of built-in support for women taking them.

Abortion pills have become even easier to get since the immediate aftermath of Dobbs v. Jackson Women’s Health Organization , with new suppliers appearing regularly and existing suppliers expanding to absorb more demand.

In the year since the research in the study was compiled, Aiken said, telehealth clinics in particular have significantly expanded their reach in antiabortion states, leading to far more abortions provided than are reflected in her study. While Europe-based Aid Access, the largest of these groups, initially relied on pharmacies in India to mail pills to patients in states with bans, the organization has now started allowing U.S.-based doctors to prescribe and mail the pills themselves, making use of “shield laws” recently passed in several Democratic-led states to protect the providers from prosecution. That change has reduced Aid Access’s shipping time from several weeks to a few days.

The organization now mails approximately 6,000 doses of medication abortion into states with abortion bans each month, according to Gomperts. She expects that number will continue to grow.

“What we know from other countries is the more this [becomes] mainstreamed, the more people will feel comfortable doing it by themselves,” she said.

Struggling to come up with a way to crack down on self-managed abortions, antiabortion advocates have taken aim at abortion pills more broadly. At Tuesday’s Supreme Court arguments, antiabortion advocates will argue that the U.S. Food and Drug Administration rushed its 2000 approval of mifepristone, the first drug in the two-step medication abortion regimen, as well as subsequent decisions to lift restrictions on the pill. Perhaps most significantly, antiabortion advocates are seeking to reinstate the requirement for people taking medication abortion to see a medical provider in person — a change that could halt the mailing of abortion pills.

“When the FDA is recklessly saying that this is safe and women don’t need or deserve ongoing care — that’s dangerous,” Christina Francis, chief executive of the American Association of Pro-Life Obstetricians and Gynecologists, said in an interview last month.

Leading studies show that medication abortions conducted via telehealth are safe. Major adverse events, such as infections or a hemorrhage, occur in less than 1 percent of cases, a figure that remains the same whether or not a patient has an ultrasound and an in-person consultation.

The upcoming Supreme Court case could have significant implications for people taking abortion pills in states with bans, potentially preventing U.S. providers from utilizing shield laws.

Abortion rights leaders say they will continue to mail pills into antiabortion states, regardless of whether it’s legal.

“The reality is that medication abortion and telemedicine will continue — but whether it continues from licensed providers, aboveboard, without stigma … is something we have to really be aware of and fighting for,” said Julie Kay, the executive director of the Abortion Coalition for Telemedicine, an abortion rights group.

U.S. abortion access, reproductive rights

Tracking abortion access in the United States: Since the Supreme Court struck down Roe v. Wade , the legality of abortion has been left to individual states. The Washington Post is tracking states where abortion is legal, banned or under threat.

Abortion pills: The Supreme Court seemed unlikely to limit access to the abortion pill mifepristone . Here’s what’s at stake in the case and some key moments from oral arguments . For now, full access to mifepristone will remain in place . Here’s how mifepristone is used and where you can legally access the abortion pill .

New study: The number of women using abortion pills to end their pregnancies on their own without the direct involvement of a U.S.-based medical provider rose sharply in the months after the Supreme Court eliminated a constitutional right to abortion , according to new research.

Abortion and the 2024 election: Voters in a dozen states in 2024 could decide the fate of abortion rights with constitutional amendments on the ballot in a pivotal election year. The Biden administration announced new steps intended to ensure access to contraception, abortion medication and emergency abortions at hospitals. Here’s what the moves on reproductive health mean for consumers. See where the 2024 presidential candidates stand on abortion bans .

  • States where abortion is legal, banned or under threat March 20, 2024 States where abortion is legal, banned or under threat March 20, 2024
  • Supreme Court skeptical of efforts to restrict access to abortion pill March 26, 2024 Supreme Court skeptical of efforts to restrict access to abortion pill March 26, 2024
  • 5 key moments from Supreme Court arguments on the abortion pill case March 26, 2024 5 key moments from Supreme Court arguments on the abortion pill case March 26, 2024

assignment for reproductive system

COMMENTS

  1. 22.2: Introduction to the Reproductive System

    The main structures of the female reproductive system are internal to the body and shown in Figure 22.2.4 22.2. 4. They include the paired ovaries, which are small, oval structures that produce eggs and secrete estrogen. The two Fallopian tubes (aka uterine tubes) start near the ovaries and end at the uterus.

  2. Human reproductive system

    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 time in the ...

  3. The reproductive system review (article)

    Male reproductive gland that produces sperm and male hormones. Ovaries. Female reproductive gland that produces eggs and female hormones. Menstrual cycle. Pattern of events in females involving the development and release of an egg. Fertilization. The process in sexual reproduction in which a male gamete and female gamete fuse to form a new cell.

  4. PDF THE REPRODUCTION SYSTEMS

    The reproductive system is a collection of internal and external organs — in both males and females — that work together for the purpose of procreating. Due to its vital role in the survival of the species, many scientists feel that the reproductive system is among the most important systems in the entire body.

  5. 27.2 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 ...

  6. 5.1 Human Reproductive Anatomy

    In the male reproductive system, the scrotum houses the testicles or testes (singular: testis), including providing passage for blood vessels, nerves, and muscles related to testicular function. The testes are gonads, and they produce sperm (the male gametes) and some reproductive hormones. Each testis is approximately 2.5 by 3.8 cm (1.5 by 1 ...

  7. 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.

  8. 23.1: Introduction to the Reproductive System

    In this chapter, you will explore the male and female reproductive systems, whose healthy functioning can culminate in the powerful sound of a newborn's first cry. Figure 23.1.1: Ovulation. This is a color photograph of the surface of an ovary. The round bulge is a follicle that will rupture soon. The rupturing of the follicle is ovulation ...

  9. Reproductive System Lab Assignment Flashcards

    Terms in this set (10) 1. Trace the pathway of the sperm from the male testes to the uterine tube of the female. Glucose also comes from starches like potatoes, our bodies produce it and every cell on earth has glucose in it. Glucose is a molecule absolutely vital to life. The testes located outside of the abdominopelvic cavity.

  10. Human Reproductive System

    The female reproductive system is active before, during and after fertilization as well. It consists of the following parts: A pair of ovaries: Ovaries produce and store ovum in them. They also produce a female hormone called estrogen. Fallopian tubes (Oviducts): They are the site of fertilization.

  11. Chapter 7:14 Reproductive System assignment sheet Flashcards

    Growth of endometrial tissue outside the uterus. Epididymitis. Inflammation of the epididymis. Orchitis. Inflammation of the testes. Herpes. STD caused by a virus and characterized by fluid filled vesicles and ulcers. Study with Quizlet and memorize flashcards containing terms like Scrotum, Testes, Epididymis and more.

  12. PDF Reproductive System

    Use Reproductive System Visuals 1-6 to continue reviewing the male and female reproductive systems, including the location and function of each part. Use a document camera (or SMART Board, overhead projector, etc) to project the images ... The assignment will be for the students who have the cards to go to the

  13. Female Reproductive System ( Read )

    The female reproductive system forms before birth but does not become capable of reproduction until it matures during puberty. The female reproductive system includes organs and other structures that produce and release eggs, secrete female sex hormones, and enable the development and birth of a fetus. Immature eggs form in the ovaries before ...

  14. AHP106 Wk6 Assignment

    AHP106 Wk2 Assignment (2) Kimberly's Chapt 7&8 - easy; MAS110 Week 1 Infection Control Worksheet; AHP106 Wk4 Assignment; AHP106 Wk3 Assignment; AHP106 Wk4 Assignment; Related documents. ... Chapter 26: Reproductive Systems Go Figure 1. Which of the following is correct according to Fig. 26? a. The epididymis is located within the pelvic cavity.

  15. Female Reproductive System

    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 ...

  16. Male Reproductive System ( Read )

    Covers the two main functions of the male reproductive system, producing sperm and secreting testosterone. Add to Library. Details. Resources. Download. Quick Tips. Notes/Highlights. Vocabulary.

  17. Chapter 8: Reproductive Systems Flashcards

    includes the testes, epididymis, vas deferens, seminal vesicles, ejaculatory duct, prostate, and penis. Female reproductive system: external organs. also known as genitalia, are collectively known as the vulva, include mons pubis, labia majora, labia minora, clitoris, and Bartholin glands. female sex hormones.

  18. Biology Assignment: Human Reproductive System Assignment

    1. Role of different structures within male and female reproductive system Female reproductive system Ovaries Ovaries are considered as the primary organs of the reproductive system. These secretes two of the very essential hormones which are important for a female body in the whole process of the reproduction (Agarwal and et.al, 2012). These involve oestrogen and progesterone.

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    Pathway Assignment: Please diagram the Hypothalamo-Pituitary-Gonadal Axis for the female reproductive; system (Label major organs clearly). Indicate pathways of the various hormones secreted. and their targets. Please include examples of negative feedback loops in your illustration. Ensure that you are including all major tissues/organs and ...

  20. Abortions outside medical system increased sharply after Roe fell

    self-managed abortions. The supply of abortion pills outside of the formal health-care setting increased sharply in the six months after Dobbs v. Jackson Women's Health Organization, a landmark ...