Chapter 26: The Reproductive System

Oogonia are

- Diploid

Gonads in a fetus develop from intermediate mesoderm.

- True

Penis

- Is a supporting structure of the male reproductive system that contains the urethra and is a passageway for the ejaculation of semen and the excretion of urine. - It is cylindrical in shape and consists of a body, glans penis, and a root. - The body of the penis is composed of three cylindrical masses of tissue, each surrounded by fibrous tissue called the tunica albuginea. - The two dorsolateral masses of the body of the penis are called the corpora cavernosa penis. The smaller midventral mass, the corpus spongiosum penis, contains the spongy urethra and keeps it open during ejaculation. - The distal end of the corpus spongiosum penis is a slightly enlarged, acorn‐shaped region called the glans penis; its margin is the corona. - The distal urethra enlarges within the glans penis and forms a terminal slitlike opening, the external urethral orifice. - Covering the glans in an uncircumcised penis is the loosely fitting prepuce (PRĒ‐poos), or foreskin. - The root of the penis is the attached portion. --> It consists of the bulb of the penis, the expanded posterior continuation of the base of the corpus spongiosum penis, and the crura of the penis, the two separated and tapered continuations of the corpora cavernosa penis. - The bulb of the penis is attached to the inferior surface of the deep muscles of the perineum and is enclosed by the bulbospongiosus muscle. - The weight of the penis is supported by two ligaments that are continuous with the fascia of the penis: (1) The fundiform ligament arises from the inferior part of the linea alba; (2) the suspensory ligament of the penis arises from the pubic symphysis. Upon sexual stimulation, parasympathetic fibers from the sacral portion of the spinal cord initiate and maintain an erection, the enlargement and stiffening of the penis. - The parasympathetic fibers produce and release and cause local production of nitric oxide (NO). - Expansion of the blood sinuses also compresses the veins that drain the penis; the slowing of blood outflow helps to maintain the erection. - The insertion of the erect penis of a male into the vagina of a female is called sexual intercourse or coitus. - The term priapism refers to a persistent and usually painful erection of the penis that does not involve sexual desire or excitement. The condition may last up to several hours and is accompanied by pain and tenderness. --> It results from abnormalities of blood vessels and nerves, usually in response to medication used to produce erections in males who otherwise cannot attain them. Other causes include a spinal cord disorder, leukemia, sickle‐cell disease, or a pelvic tumor. - Ejaculation, the powerful release of semen from the urethra to the exterior, is a sympathetic reflex coordinated by the lumbar portion of the spinal cord. - As part of the reflex, the smooth muscle sphincter at the base of the urinary bladder closes. - Even before ejaculation occurs, peristaltic contractions in the ampulla of the ductus deferens, seminal vesicles, ejaculatory ducts, and prostate propel semen into the penile portion of the urethra (spongy urethra). - Typically, this leads to emission, the discharge of a small volume of semen before ejaculation. - Emission may also occur during sleep. The musculature of the penis (bulbospongiosus, ischiocavernosus, and superficial transverse perineal muscles), which is supplied by the pudendal nerves, also contracts at ejaculation. - Once sexual stimulation of the penis has ended, the arterioles supplying the erectile tissue of the penis constrict and the smooth muscle within erectile tissue contracts, making the blood sinuses smaller. - This relieves pressure on the veins draining the penis and allows the blood to drain through them. Consequently, the penis returns to its flaccid (relaxed) state. - A premature ejaculation is ejaculation that occurs too early, for example, during foreplay or upon or shortly after penetration. It is usually caused by anxiety, other psychological causes, or an unusually sensitive foreskin or glans penis. For most males, premature ejaculation can be overcome by various mechanical techniques (such as squeezing the penis between the glans penis and shaft as ejaculation approaches), behavioral therapy, or medication.

The tunica vaginalis a

- Serous membrane

Which organ is part of the duct system that transports sperm to the exterior?

- Urethra

What is the effect of GnRH during the female reproductive cycle? 1. stimulates release of FSH from the pituitary 2. stimulates release of LH from the pituitary

- 1 and 2

Decreased male sex drives typically occur about the age of

- 55

Testes

- AKA testicles, are paired oval glands in the scrotum measuring about 5 cm (2 in.) long and 2.5 cm (1 in.) in diameter. Each testis (singular) weighs 10-15 grams. - The testes develop near the kidneys, in the posterior portion of the abdomen, and they usually begin their descent into the scrotum through the inguinal canals during the latter half of the seventh month of fetal development. - The testes are partially covered by a serous membrane called the tunica vaginalis, which is derived from the peritoneum and forms during the descent of the testes. - Like other serous membranes, it has a visceral layer and a parietal layer and forms a fist‐in‐balloon relationship with the testis. - A collection of serous fluid in the cavity of the tunica vaginalis is called a hydrocele. - Internal to the visceral layer of the tunica vaginalis, the testis is surrounded by a white fibrous capsule composed of dense irregular connective tissue, the tunica albuginea; it extends inward, forming septa that divide each testis into a series of internal compartments called lobules. - Each of the 200-300 lobules contains one to three tightly coiled tubules, the seminiferous tubules, where sperm are produced. - The process by which the seminiferous tubules of the testes produce sperm is called spermatogenesis. - The walls of the seminiferous tubules contain two types of cells: spermatogenic cells, the sperm‐forming cells, and sustentacular cells or Sertoli cells, which have several functions in supporting spermatogenesis. - Starting at puberty, sperm production begins at the periphery of the seminiferous tubules in stem cells called spermatogonia. - These cells develop from primordial germ cells that arise from the yolk sac endoderm and enter the testes during the fifth week of development. - Toward the lumen of the tubule are layers of progressively more mature cells. In order of advancing maturity, these are primary spermatocytes, secondary spermatocytes, spermatids, and sperm cells. - After a sperm cell, or spermatozoon, has formed, it is released into the lumen of the seminiferous tubule. - Internal to the basement membrane and spermatogonia, tight junctions join neighboring sustentacular cells to one another. - These junctions form an obstruction known as the blood-testis barrier because substances must pass through the sustentacular cells before they can reach the developing sperm. - By isolating the developing gametes from the blood, the blood-testis barrier prevents an immune response against the spermatogenic cell's surface antigens, which are recognized as "foreign" by the immune system. The blood-testis barrier does not include spermatogonia. - In the spaces between adjacent seminiferous tubules are clusters of cells called interstitial cells or Leydig cells. - These cells secrete testosterone, the most important androgen. An androgen is a hormone that promotes the development of masculine characteristics. Testosterone also promotes a man's libido (sex drive). - In meiosis I, homologous pairs of chromosomes line up at the metaphase plate, and crossing‐over occurs. - Then the meiotic spindle pulls one (duplicated) chromosome of each pair to an opposite pole of the dividing cell. The two cells formed by meiosis I are called secondary spermatocytes. Each secondary spermatocyte has 23 chromosomes, the haploid number (n). - Each chromosome within a secondary spermatocyte, however, is made up of two chromatids (two copies of the DNA) still attached by a centromere. No replication of DNA occurs in the secondary spermatocytes. - In meiosis II, no replication of DNA occurs. The chromosomes line up in single file along the metaphase plate, and the two chromatids of each chromosome separate. The four haploid cells resulting from meiosis II are called spermatids. A single primary spermatocyte therefore produces four spermatids through two rounds of cell division (meiosis I and meiosis II).

The vagina is lined with _________ whereas the uterine/fallopian tubes are lined with ________.

- Moist stratified squamous; ciliated simple columnar

Which structure produces the hormone relaxin?

- Ovary

1 out of 3 aging males may develop enlargement of:

- Prostate

Female reproductive cycle

- The ovarian cycle is a series of events in the ovaries that occur during and after the maturation of an oocyte. Steroid hormones released by the ovaries control the uterine cycle, a concurrent series of changes in the endometrium of the uterus to prepare it for the arrival and development of a fertilized ovum. - The general term female reproductive cycle encompasses the ovarian and uterine cycles, the hormonal changes that regulate them, and the related cyclical changes in the breasts and cervix. - Gonadotropin‐releasing hormone (GnRH) secreted by the hypothalamus controls the events of the female reproductive cycle. - GnRH stimulates the release of follicle‐stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. - FSH in turn initiates follicular growth and the secretion of estrogens by the growing ovarian follicles. - LH stimulates the further development of follicles and their full secretion of estrogens. - At midcycle, LH triggers ovulation and then promotes formation of the corpus luteum (the reason for the name luteinizing hormone). - Stimulated by LH, the corpus luteum produces and secretes estrogens, progesterone, relaxin, and inhibin.

Seminal vesicles

- The paired seminal vesicles or seminal glands are convoluted pouchlike structures, about 5 cm (2 in.) in length, lying posterior to and at the base of the urinary bladder anterior to the rectum - Through the seminal vesicle ducts they secrete an alkaline, viscous fluid that contains fructose, prostaglandins, and clotting proteins unlike those found in blood. - The alkaline nature of the fluid helps to neutralize the acidic environment of the male urethra and female reproductive tract that otherwise would inactivate and kill sperm. The fructose is used for the production of ATP by sperm. - Prostaglandins contribute to sperm motility and viability and may also stimulate muscular contractions within the female reproductive tract. The clotting proteins help semen coagulate after ejaculation.

Abortion

- Abortion refers to the premature expulsion of the products of conception from the uterus, usually before the twentieth week of pregnancy. An abortion may be spontaneous or induced. - Mifepristone, also known as RU 486. It is a hormone approved only for pregnancies 9 weeks or less when taken with a misopostol (a prostaglandin). Mifepristone is an antiprogestin; it blocks the action of progesterone by binding to and blocking progesterone receptors. Progesterone prepares the uterine endometrium for implantation and then maintains the uterine lining after implantation. - Another type of induced abortion is called vacuum aspiration (suction) and can be performed up to the sixteenth week of pregnancy. A small, flexible tube attached to a vacuum source is inserted into the uterus through the vagina. The embryo or fetus, placenta, and lining of the uterus are then removed by suction. - For pregnancies between 13 and 16 weeks, a technique called dilation and evacuation is commonly used. After the cervix is dilated, suction and forceps are used to remove the fetus, placenta, and uterine lining. From the 16th to 24th week, a late‐stage abortion may be induced using surgical methods similar to dilation and evacuation or nonsurgical methods utilizing a saline solution or medications.

The only true method of birth control that is 100% effective is

- Abstinence

At the onset of menarche, ovulation fails to occur _____% of the time.

- 90

What are the end products of the first meiotic division (meiosis I) in oogenesis?

- A secondary oocyte and first polar body

Non-incisional sterilization

- An alternative to tubal ligation. In the Essure® procedure, a soft coil made of polyester fibers and metals is inserted with a catheter into the vagina, through the uterus, and into each uterine tube. Over a three‐month period, the insert stimulates the growth of scar tissue in and around itself, blocking the uterine tubes. --> As with tubal ligation, the secondary oocyte cannot pass through the uterine tubes, and sperm cannot reach the oocyte. Unlike tubal ligation, non‐incistional sterilazation does not require general anesthesia.

Intrauterine devices

- An intrauterine device (IUD) is a small object made of plastic, copper, or stainless steel that is inserted by a health‐care professional into the cavity of the uterus. IUDs prevent fertilization from taking place by blocking sperm from entering the uterine tubes.

Ovaries

- Are paired glands that resemble unshelled almonds in size and shape; they are the female gonads and are homologous to the testes. - The ovaries, one on either side of the uterus, descend to the brim of the superior portion of the pelvic cavity during the third month of development. - The broad ligament of the uterus, which is a fold of the peritoneum, attaches to the ovaries by a subset of this peritoneal fold called the mesovarium. - The ovarian ligament anchors the ovaries to the uterus, and the suspensory ligament attaches them to the pelvic wall. - Each ovary contains a hilum, the point of entrance and exit for blood vessels and nerves along which the mesovarium is attached.

Uterine tubes

- Females have two uterine tubes, also called fallopian tubes or oviducts, that extend laterally from the uterus. - The tubes, which measure about 10 cm (4 in.) long and lie within the folds of the broad ligaments of the uterus, transport secondary oocytes and fertilized ova from the ovaries to the uterus. - (This portion of the broad ligament is called the mesosalpinx.) - The funnel‐shaped portion of each uterine tube, called the infundibulum, is close to the ovary but is open to the peritoneal cavity. It ends in a fringe of fingerlike projections called fimbriae, one of which is attached to the lateral end of the ovary. - From the infundibulum, the uterine tube extends medially and eventually inferiorly and attaches to the superior lateral angle of the uterus. - The ampulla of the uterine tube is the widest, longest portion, making up about the lateral two‐thirds of its length. - The isthmus of the uterine tube is the more medial, short, narrow, thick‐walled portion that joins the uterus.

Hot flashes between the ages of 40 and 50 in most women are associated with bursts releases of

- GnRH

Pulses of __________ initiate changes associated with puberty.

- GnRH

The intermediate mesoderm gives rise to the __________, which develop into gonads.

- Gonadal ridges

The vagina histology

- The mucosa of the vagina is continuous with that of the uterus. Histologically, it consists of nonkeratinized stratified squamous epithelium and lamina propria that lies in a series of transverse folds called rugae. - The mucosa of the vagina contains large stores of glycogen, the decomposition of which produces organic acids. - The resulting acidic environment retards microbial growth, but it is also harmful to sperm. - Alkaline components of semen, mainly from the seminal vesicles, raise the pH of fluid in the vagina and increase viability of the sperm. - A thin fold of vascularized mucous membrane, called the hymen, forms a border around and partially closes the inferior end of the vaginal opening to the exterior, the vaginal orifice. - After its rupture, usually following the first sexual intercourse, only remnants of the hymen remain. - Sometimes the hymen completely covers the orifice, a condition called imperforate hymen. Surgery may be needed to open the orifice and permit the discharge of menstrual flow.

Bulbourethral glands

- The paired bulbourethral glands, or Cowper's glands, each about the size of a pea, lie inferior to the prostate on either side of the membranous urethra within the deep muscles of the perineum; their ducts open into the spongy urethra. - During sexual arousal, the bulbourethral glands secrete an alkaline substance that protects the passing sperm by neutralizing acids from urine in the urethra. - At the same time, they secrete mucus that lubricates the end of the penis and the lining of the urethra, thereby decreasing the number of sperm damaged during ejaculation.

The uterus

- The uterus (womb) serves as part of the pathway for sperm deposited in the vagina to reach the uterine tubes. - It is also the site of implantation of a blastocyst, development of the fetus during pregnancy, and labor. - During reproductive cycles when implantation does not occur, the uterus is the source of menstrual flow. - Anatomical subdivisions of the uterus include the following: (1) a dome‐shaped portion superior to the uterine tubes called the fundus, (2) a tapering central portion called the body, and (3) an inferior narrow portion called the cervix that opens into the vagina. - Between the body of the uterus and the cervix is the isthmus, a constricted region about 1 cm (0.5 in.) long. - The interior of the body of the uterus is called the uterine cavity, and the interior of the narrow cervix is called the cervical canal. - The cervical canal opens into the uterine cavity at the internal os and into the vagina at the external os. - Normally, the body of the uterus projects anteriorly and superiorly over the urinary bladder in a position called anteflexion. - The paired broad ligaments are double folds of peritoneum attaching the uterus to either side of the pelvic cavity. - The paired uterosacral ligaments, also peritoneal extensions, lie on either side of the rectum and connect the uterus to the sacrum. - The cardinal (lateral cervical) ligaments are located inferior to the bases of the broad ligaments and extend from the pelvic wall to the cervix and vagina. - The round ligaments are bands of fibrous connective tissue between the layers of the broad ligament; they extend from a point on the uterus just inferior to the uterine tubes to a portion of the labia majora of the external genitalia. - A posterior tilting of the uterus, called retroflexion, is a harmless variation of the normal position of the uterus. There is often no cause for the condition, but it may occur after childbirth or because of an ovarian cyst.

The vagina

- The vagina is a tubular, fibromuscular canal lined with mucous membrane that extends from the exterior of the body to the uterine cervix. - Situated posterior to the urinary bladder and urethra and anterior to the rectum, the vagina is directed superiorly and posteriorly, to attach to the cervix of the uterus. - A recess called the fornix surrounds the vaginal attachment to the cervix. When properly inserted, a contraceptive diaphragm rests in the fornix, where it is held in place as it covers the cervix.

Barrier methods

- Usa physical barrier to prevent sperm from gaining access to the uterine cavity and uterine tubes. In addition to preventing pregnancy, certain barrier methods (male condom and vaginal pouch) may also provide some protection against sexually transmitted diseases (STDs) such as AIDS. In contrast, oral contraceptives and IUDs confer no such protection. Among the barrier methods are the male condom, vaginal pouch, diaphragm, and cervical cap. - A male condom is a nonporous, latex covering placed over the penis that prevents deposition of sperm in the female reproductive tract. - A vaginal pouch, sometimes called a female condom, is designed to prevent sperm from entering the uterus. It is made of two flexible rings connected by a polyurethane sheath. One ring lies inside the sheath and is inserted to fit over the cervix; the other ring remains outside the vagina and covers the female external genitals. - A diaphragm is a rubber, dome‐shaped structure that fits over the cervix and is used in conjunction with a spermicide. It can be inserted by the female up to 6 hours before intercourse. The diaphragm stops most sperm from passing into the cervix, and the spermicide kills most sperm that do get around it. Although diaphragm use does decrease the risk of some STDs, it does not fully protect against HIV infection because the vagina is still exposed. - A cervical cap resembles a diaphragm but is smaller and more rigid. It fits snugly over the cervix and must be fitted by a health‐care professional. Spermicides should be used with the cervical cap.

Spermicides

- Various foams, creams, jellies, suppositories, and douches that contain sperm‐killing agents, or spermicides, make the vagina and cervix unfavorable for sperm survival and are available without prescription. - They are placed in the vagina before sexual intercourse. The most widely used spermicide is nonoxynol‐9, which kills sperm by disrupting their plasma membranes. A spermicide is more effective when used with a barrier method such as a male condom, vaginal pouch, diaphragm, or cervical cap.

Ductus deferens

- Within the tail of the epididymis, the ductus epididymis becomes less convoluted, and its diameter increases. Beyond this point, the duct is referred to as the ductus deferens or vas deferens. - The ductus deferens, which is about 45 cm (18 in.) long, ascends along the posterior border of the epididymis, through the spermatic cord to the point in the lower abdominal wall where it passes through the inguinal canal to enter the pelvic cavity; there it loops over the ureter and passes over the side and down the posterior surface of the urinary bladder. - The dilated terminal portion of the ductus deferens is known as the ampulla. The mucosa of the ductus deferens consists of pseudostratified columnar epithelium and lamina propria. - Functionally, the ductus deferens conveys sperm during sexual arousal from the epididymis toward the urethra by peristaltic contractions of its muscular coat. Like the epididymis, the ductus deferens also can store sperm for several months. Any stored sperm that are not ejaculated by that time are eventually reabsorbed.

Development of the reproductive systems

-- The male and female gonads develop from gonadal ridges that arise from growth of the intermediate mesoderm. - During the fifth week of development, the gonadal ridges appear as bulges just medial to the mesonephros (intermediate kidney). - Adjacent to the gonads are the mesonephric ducts or Wolffian ducts, which eventually develop into structures of the reproductive system in males. - A second pair of ducts, the paramesonephric ducts or Müllerian ducts, develop lateral to the mesonephric ducts and eventually form structures of the reproductive system in females. Both sets of ducts empty into the urogenital sinus. - The male pattern of development is initiated by a Y chromosome "master switch" gene named SRY, which stands for Sex‐determining Region of the Y chromosome. When the SRY gene is expressed during development, its protein product causes the primitive sustentacular cells to begin to differentiate in the testes during the seventh week. The developing sustentacular cells secrete a hormone called Müllerian‐inhibiting substance (MIS), which causes apoptosis of cells within the paramesonephric (Müllerian) ducts. - Stimulated by human chorionic gonadotropin (hCG), primitive interstital (Leydig) cells in the testes begin to secrete the androgen testosterone during the eighth week. Testosterone then stimulates development of the mesonephric duct on each side into the epididymis, ductus (vas) deferens, ejaculatory duct, and seminal vesicle. The testes connect to the mesonephric duct through a series of tubules that eventually become the seminiferous tubules. The prostate and bulbourethral glands are endodermal outgrowths of the urethra. - The distal ends of the paramesonephric ducts fuse to form the uterus and vagina, and the unfused proximal portions become the uterine (fallopian) tubes. The mesonephric ducts degenerate without contributing any functional structures to the female reproductive system because testosterone is absent. The greater and lesser vestibular glands develop from endodermal outgrowths of the vestibule. - The external genitals of both male and female embryos (penis and scrotum in males and clitoris, labia, and vaginal orifice in females) also remain undifferentiated until about the eighth week. Before differentiation, all embryos have the following external structures: 1. Urethral (urogenital) folds. These paired structures develop from mesoderm in the cloacal region. 2. Urethral groove. An indentation between the urethral folds, which is the opening into the urogenital sinus. 3. Genital tubercle. A rounded elevation just anterior to the urethral folds. 4. Labioscrotal swelling. Paired, elevated structures lateral to the urethral folds. - In male embryos, some testosterone is converted to a second androgen called dihydrotestosterone (DHT). DHT stimulates development of the urethra, prostate, and external genitals (scrotum and penis). Part of the genital tubercle elongates and develops into a penis. - The urethral folds remain open as the labia minora, and the labioscrotal swellings become the labia majora. The urethral groove becomes the vestibule. After birth, androgen levels decline because hCG is no longer present to stimulate secretion of testosterone.

When a primary oocyte completes meiosis I, a secondary oocyte and a/an ____________ are produced.

- First polar body

Ovaries (histology)

•The ovarian mesothelium or surface epithelium is a layer of simple epithelium (low cuboidal or squamous) that covers the surface of the ovary. It is continuous with the mesothelium of the mesovarium and peritoneum. •The tunica albuginea is a whitish capsule of dense, irregular connective tissue immediately deep to the ovarian mesothelium. •The ovarian cortex is a region just deep to the tunica albuginea. It consists of ovarian follicles surrounded by dense irregular connective tissue that contains collagen fibers and fibroblast‐like cells called stromal cells. •The ovarian medulla is deep to the ovarian cortex. The border between the cortex and medulla is indistinct, but the medulla consists of more loosely arranged connective tissue and contains blood vessels, lymphatic vessels, and nerves. •Ovarian follicles are located in the ovarian cortex and consist of oocytes in various stages of development, plus the cells surrounding them. When the surrounding cells form a single layer, they are called follicular cells; later in development, when they form several layers, they are referred to as granulosa cells. The surrounding cells nourish the developing oocyte and begin to secrete estrogens as the follicle grows larger. •A mature (graafian) follicle is a large, fluid‐filled follicle that is ready to rupture and expel its secondary oocyte, a process known as ovulation. •A corpus luteum (=yellow body) contains the remnants of a mature follicle after ovulation. The corpus luteum produces progesterone, estrogens, relaxin, and inhibin until it degenerates into fibrous scar tissue called the corpus albicans.

Hormonal methods

- Aside from complete abstinence or surgical sterilization, hormonal methods are the most effective means of birth control. --> Oral contraceptives (the pill) contain hormones designed to prevent pregnancy. Some, called combined oral contraceptives (COCs), contain both progestin (hormone with actions similar to progesterone) and estrogens. - Oral hormonal methods of contraception include the following: • Combined pill. Contains both progestin and estrogens and is typically taken once a day for 3 weeks to prevent pregnancy and regulate the menstrual cycle. The pills taken during the fourth week are inactive (do not contain hormones) and permit menstruation to occur. An example is Yasmin.® • Extended cycle birth control pill. Contains both progestin and estrogens and is taken once a day in 3‐month cycles of 12 weeks of hormone‐containing pills followed by 1 week of inactive pills. Menstruation occurs during the thirteenth week. An example is Seasmale.® • Minipill. Contains progestin only and is taken every day of the month. An example is Minocat.® - A number of non‐oral hormonal methods of contraception are also available: • Contraceptive skin patch (Ortho Evra®). Contains both progestin and estrogens delivered in a skin patch placed on the skin (upper outer arm, back, lower abdomen, or buttocks) once a week for 3 weeks. After 3 weeks, the patch is removed from one location and then a new one is placed elsewhere. During the fourth week no patch is used. • Vaginal contraceptive ring (NuvaRing®). A flexible doughnut‐shaped ring about 5 cm (2 in.) in diameter that contains estrogens and progesterone and is inserted by the user into the vagina. It is left in the vagina for 3 weeks to prevent conception and then removed for 1 week to permit menstruation. • Emergency contraception (EC) (morning‐after pill). Consists of progestin and estrogens or progestin alone to prevent pregnancy following unprotected sexual intercourse. The relatively high levels of progestin and estrogens in EC pills provide inhibition of FSH and LH secretion. Loss of the stimulating effects of these gonadotropic hormones causes the ovaries to cease secretion of their own estrogens and progesterone. In turn, declining levels of estrogens and progesterone induce shedding of the uterine lining, thereby blocking implantation. One pill is taken as soon as possible but within 72 hours of unprotected sexual intercourse. The second pill must be taken 12 hours after the first. The pills work in the same way as regular birth control pills. • Hormone injections (Depo‐provera®). An injectable progestin given intramuscularly by a health‐care practitioner once every 3 months.

Ovulation

- At ovulation, the secondary oocyte is expelled into the peritoneal cavity together with the first polar body and corona radiata. - Normally these cells are swept into the uterine tube. If fertilization does not occur, the cells degenerate. However, if sperm are present in the uterine tube and one penetrates the secondary oocyte, meiosis II resumes. - The secondary oocyte splits into two haploid cells, again of unequal size. The larger cell is the ovum, or mature egg; the smaller one is the second polar body. - The nuclei of the sperm cell and the ovum then unite, forming a diploid zygote. If the first polar body undergoes another division to produce two polar bodies, then the primary oocyte ultimately gives rise to three haploid polar bodies, which all degenerate, and a single haploid ovum. - Thus, one primary oocyte gives rise to a single gamete (an ovum).

Most of the female germ cells degenerate before birth; this process is called

- Atresia

Birth control

- Birth control or contraception refers to restricting the number of children by various methods designed to control fertility and prevent conception.

What is the name of the structure labeled with the arrow?

- Clitoris

Which of the following act(s) to maintain optimal temperature conditions for sperm production and survival?

- Cremaster and dartos muscles

FSH is released from the anterior pituitary

- During the proliferation phase in uterus

Follicular development

- During this arrested stage of development, each primary oocyte is surrounded by a single layer of flat follicular cells, and the entire structure is called a primordial follicle. - The ovarian cortex surrounding the primordial follicles consists of collagen fibers and fibroblast‐like stromal cells. - At birth, approximately 200,000 to 2,000,000 primary oocytes remain in each ovary. Of these, about 40,000 are still present at puberty, and around 400 will mature and ovulate during a woman's reproductive lifetime. The remainder of the primary oocytes undergo atresia. - In a secondary follicle, the theca differentiates into two layers: (1) the theca interna, a highly vascularized internal layer of cuboidal secretory cells that secrete estrogens, and (2) the theca externa, an outer layer of stromal cells and collagen fibers. - In addition, the granulosa cells begin to secrete follicular fluid, which builds up in a cavity called the antrum in the center of the secondary follicle. The innermost layer of granulosa cells becomes firmly attached to the zona pellucida and is now called the corona radiata. - The secondary follicle eventually becomes larger, turning into a mature follicle. While in this follicle, and just before ovulation, the diploid primary oocyte completes meiosis I, producing two haploid (n) cells of unequal size—each with 23 chromosomes (Figure 26.15). --> The smaller cell produced by meiosis I, called the first polar body, is essentially a packet of discarded nuclear material. The larger cell, known as the secondary oocyte, receives most of the cytoplasm. Once a secondary oocyte is formed, it begins meiosis II but then stops in metaphase. The mature (graafian) follicle soon ruptures and releases its secondary oocyte, a process known as ovulation.

The mammary glands

- Each breast is a hemispheric projection of variable size anterior to the pectoralis major and serratus anterior muscles and attached to them by a layer of fascia composed of dense irregular connective tissue. - Each breast has one pigmented projection, the nipple, which has a series of closely spaced openings of ducts called lactiferous ducts, where milk emerges. - Within each breast is a mammary gland, a modified sudoriferous gland that produces milk. - A mammary gland consists of 15 to 20 lobes, or compartments, separated by a variable amount of adipose tissue. - In each lobe are several smaller compartments called lobules, composed of grapelike clusters of milk‐secreting glands termed alveoli embedded in connective tissue. - Contraction of myoepithelial cells surrounding the alveoli helps propel milk toward the nipples. When milk is being produced, it passes from the alveoli into a series of secondary tubules and then into the mammary ducts. - Near the nipple, the mammary ducts expand slightly to form sinuses called lactiferous sinuses, where some milk may be stored before draining into a lactiferous duct. - Each lactiferous duct typically carries milk from one of the lobes to the exterior.

Ejaculatory duct

- Each ejaculatory duct is about 2 cm (1 in.) long and is formed by the union of the duct from the seminal vesicle and the ampulla of the ductus deferens. - The short ejaculatory ducts form just superior to the base (superior portion) of the prostate and pass inferiorly and anteriorly through the prostate. - They terminate in the prostatic urethra, where they eject sperm and seminal vesicle secretions just before the release of semen from the urethra to the exterior.

Uterine tubes histology

- Histologically, the uterine tubes are composed of three layers: mucosa, muscularis, and serosa. - The mucosa consists of epithelium and lamina propria (areolar connective tissue). - The epithelium contains ciliated simple columnar cells, which function as a ciliary "conveyor belt" to help move a fertilized ovum within the tube toward the uterus, and nonciliated cells called peg cells, which have microvilli and secrete a fluid that provides nutrition for the ovum. - The middle layer, the muscularis, is composed of an inner, thick, circular ring of smooth muscle and an outer, thin region of longitudinal smooth muscle. - Peristaltic contractions of the muscularis and the ciliary action of the mucosa help move the oocyte or fertilized ovum toward the uterus. The outer layer of the uterine tubes is a serous membrane, the serosa. - Fertilization can occur up to about 24 hours after ovulation. - Some hours after fertilization, the nuclear materials of the haploid ovum and sperm unite. The diploid fertilized ovum is now called a zygote and begins to undergo cell divisions while moving toward the uterus. --> It arrives in the uterus 6 to 7 days after ovulation. Unfertilized secondary oocytes disintegrate. - The uterine tubes are supplied by branches of the uterine arteries and ovarian arteries. - Venous return is via the uterine veins. - The uterine tubes are supplied with sympathetic and parasympathetic nerve fibers from the hypogastric plexus and the pelvic splanchnic nerves. - The fibers are distributed to the muscular coat of the tubes and their blood vessels.

The uterus histology

- Histologically, the uterus consists of three layers of tissue: the perimetrium, myometrium, and endometrium. - The outer layer—the perimetrium; or serosa—is part of the peritoneum; it is composed of simple squamous epithelium and a thin layer of areolar connective tissue. - Laterally, the peritoneum becomes the broad ligament. - Anteriorly, the peritoneum covers the urinary bladder and forms a shallow pouch, the vesicouterine pouch between the urinary bladder and the uterus. - Posteriorly, the peritoneum covers the rectum and forms a deep pouch between the uterus and the rectum, the rectouterine pouch or pouch of Douglas—the most inferior point in the peritoneal cavity. - The middle layer of the uterus, the myometrium, consists of three layers of smooth muscle fibers that are thickest in the fundus and thinnest in the cervix. The thicker middle layer is circular; the inner and outer layers are longitudinal or oblique. - During labor and childbirth, coordinated contractions of the myometrium in response to stimulation by the hormone oxytocin from the posterior pituitary help expel the fetus from the uterus.

Urethra

- In males, the urethra is the shared terminal duct of the reproductive and urinary systems; it serves as a passageway for both semen and urine. - The prostatic urethra passes through the prostate. As this duct continues inferiorly, it passes through the deep muscles of the perineum, where it is known as the intermediate (membranous) urethra. - The intermediate urethra is about 1 cm (0.5 in.) in length. - As this duct passes through the corpus spongiosum of the penis, it is known as the spongy (penile) urethra, which is about 15-20 cm (6-8 in.) long. The spongy urethra ends at the external urethral orifice.

Female reproductive system

- Include the ovaries, which produce secondary oocytes and hormones such as progesterone and estrogens, inhibin, and relaxin; the uterine tubes, or oviducts, which transport secondary oocytes and fertilized ova to the uterus; the uterus, in which embryonic and fetal development occur; the vagina; and external organs that constitute the vulva, or pudendum. - The mammary glands also are considered part of the female reproductive system.

Small plastic objects placed in the uterine cavity that prevent fertilization by blocking sperm are

- Intrauterine devices

Which follicle type releases a cell which is still in meiosis II from the ovary during ovulation?

- Mature follicle

The permanent loss of menses is called _____________.

- Menopause

Abstinence

- No single, ideal method of birth control exists. The only method of preventing pregnancy that is 100 percent reliable is complete abstinence, the avoidance of sexual intercourse.

Which ovarian structure contains oocytes in various stages of development?

- Ovarian follicles

Which structures begin on either side of the uterus and then descend to the superior portion of the pelvic cavity during the third month of development?

- Ovaries

The release of the secondary oocyte into the peritoneal cavity occurs during which phase of the menstrual cycle?

- Ovulation

Ovulation

- Ovulation, the rupture of the mature (graafian) follicle and the overlying germinal epithelium of the ovary and the release of the secondary oocyte into the peritoneal cavity, usually occurs on day 14 in a 28‐day cycle. - During ovulation, the secondary oocyte remains surrounded by its zona pellucida and corona radiata. Development of a secondary follicle into a fully mature follicle generally takes a total of about 20 days. - During this time the primary oocyte completes meiosis I to become a secondary oocyte; the secondary oocyte then begins meiosis II but halts in metaphase until it is fertilized. From time to time, an oocyte is lost into the peritoneal cavity, where it later disintegrates. - The small amount of blood that sometimes leaks into the peritoneal cavity from the ruptured follicle can cause pain, known as mittelschmerz, at the time of ovulation.

The female reproductive tract develops from

- Paramesonephric ducts

Ducts of the testis

- Pressure generated by the fluid secreted by sustentacular cells pushes sperm and fluid along the lumen of seminiferous tubules and then into a series of very short ducts called straight tubules. - The straight tubules lead to a network of ducts in the testis called the rete testis. - From the rete testis, sperm move into a series of coiled efferent ducts in the epididymis that empty into a single tube called the ductus epididymis.

The secretory phase of the female reproductive cycle is controlled by the release of _____________ from the ovary.

- Progesterone

Aging and the reproductive systems

- Puberty is the period when secondary sexual characteristics begin to develop and the potential for sexual reproduction is reached. The onset of puberty is marked by pulses or bursts of LH and FSH secretion, each triggered by a pulse of GnRH. Most pulses occur during sleep. As puberty advances, the hormone pulses occur during the day as well as at night. The pulses increase in frequency during a 3‐ to 4‐year period until the adult pattern is established. The stimuli that cause the GnRH pulses are still unclear, but a role for the hormone leptin is starting to unfold. Just before puberty, leptin levels rise in proportion to adipose tissue mass. Interestingly, leptin receptors are present in both the hypothalamus and anterior pituitary. - In females, the reproductive cycle normally occurs once each month from menarche (me‐NAR‐kē), the first menses, to menopause, the permanent cessation of menses. Thus, the female reproductive system has a time‐limited span of fertility between menarche and menopause. For the first 1 to 2 years after menarche, ovulation occurs in only about 10 percent of the cycles and the luteal phase is short. - In males, declining reproductive function is much more subtle than in females. Healthy men often retain reproductive capacity into their eighties or nineties. At about age 55 a decline in testosterone synthesis leads to reduced muscle strength, fewer viable sperm, and decreased sexual desire. Although sperm production decreases 50-70 percent between ages 60 and 80, abundant sperm may still be present even in old age. - Enlargement of the prostate to two to four times its normal size occurs in approximately one‐third of all males over age 60. This condition, called benign prostatic hyperplasia (BPH), decreases the size of the prostatic urethra and is characterized by frequent urination, nocturia (bed‐wetting), hesitancy in urination, decreased force of urinary stream, postvoiding leakage, and a sensation of incomplete emptying.

During ovulation, what structure is discharged from the ovary?

- Secondary oocyte

The products of meiosis I during spermatogenesis are

- Secondary spermatocytes

Semen

- Semen is a mixture of sperm and seminal fluid, a liquid that consists of the secretions of the seminiferous tubules, seminal vesicles, prostate, and bulbourethral glands. - A male whose sperm count falls below 20 million/mL is likely to be infertile. The very large number is required for successful fertilization because only a tiny fraction ever reach the secondary oocyte, whereas too many sperm without sufficient dilution from seminal fluid results in infertility because the sperm tails tangle and lose motility. - The presence of blood in semen is called hemospermia. In most cases, it is caused by inflammation of the blood vessels lining the seminal vesicles; it is usually treated with antibiotics.

When some of the ductus deferens is removed,

- Sperm cannot leave the male reproductive tract

Sperm

- Spermatogenesis produces about 300 million sperm per day. - The major parts of a sperm are the head and the tail. The flattened, pointed head of the sperm is about 4-5 μm long. It contains a nucleus that has highly condensed haploid chromosomes (23). - Covering the anterior two‐thirds of the nucleus is the acrosome, a caplike vesicle filled with enzymes that help a sperm to penetrate a secondary oocyte to bring about fertilization. - Among the enzymes are hyaluronidase and proteases. - The tail of a sperm is subdivided into four parts: neck, middle piece, principal piece, and end piece. - The neck is the constricted region just behind the head that contains centrioles. - The centrioles form the microtubules that comprise the remainder of the tail. The middle piece contains mitochondria arranged in a spiral, which provide the energy (ATP) for locomotion of sperm to the site of fertilization and for sperm metabolism. - The principal piece is the longest portion of the tail and the end piece is the terminal, tapering portion of the tail. Once ejaculated, most sperm do not survive more than 48 hours within the female reproductive tract.

In the figure shown, what structure is indicated? (Diagram of the male urinary tract)

- Spongy urethra

After a vasectomy, sperm production

- Stays the same

Surgical sterilization

- Sterilization is a procedure that renders an individual incapable of further reproduction. --> The principal method for sterilization of males is a vasectomy, in which a portion of each ductus deferens is removed. In order to gain access to the ductus deferens, an incision is made with a scalpel (conventional procedure) or a puncture is made with special forceps (non‐scalpel vasectomy). - Sterilization in females most often is achieved by performing a tubal ligation in which both uterine tubes are tied closed and then cut. --> This can be achieved in a few different ways. "Clips" or "clamps" can be placed on the uterine tubes, the tubes can be tied and/or cut, and sometimes the tubes are cauterized. In any case, the result is that the secondary oocyte cannot pass through the uterine tubes, and sperm cannot reach the oocyte.

How do oral contraceptives work to reduce the likelihood of pregnancy?

- Suppressing FSH and LH levels

What is the name of the structure labeled with the arrow?

- Testes

The gonads

- Testes in males and ovaries in females—produce gametes and secrete sex hormones. - Various ducts then store and transport the gametes, and accessory sex glands produce substances that protect the gametes and facilitate their movement. - Finally, supporting structures, such as the penis in males and the vagina in females, assist the delivery of gametes, and the uterus in females assists in the growth of the embryo and fetus during pregnancy.

Gynecology

- The branch of medicine dealing with disorders and treatment of the reproductive system in women.

Andrology

- The branch of medicine that deals with male disorders, especially infertility and sexual dysfunction, is called andrology

Andrology

- The branch of medicine that deals with male disorders, especially infertility and sexual dysfunction.

Accessory sex glands in males

- The ducts of the male reproductive system store and transport sperm cells, but the accessory sex glands secrete most of the liquid portion of semen. The accessory sex glands include the seminal vesicles, the prostate, and the bulbourethral glands.

Epididymis

- The epididymis is a comma‐shaped organ about 4 cm (1.5 in.) long that curves along the superior and posterior border of each testis having a comma‐shape in profile. - Each epididymis consists mostly of the tightly coiled ductus epididymis. The efferent ducts from the testis join the ductus epididymis at the larger, superior portion of the epididymis called the head. - The body is the narrow midportion of the epididymis, and the tail is the smaller, inferior portion. At its distal end, the tail of the epididymis continues as the ductus (vas) deferens. - The free surfaces of the columnar cells contain stereocilia, long, branching microvilli that increase surface area for the reabsorption of degenerated sperm. - Connective tissue around the muscle layer attaches the loops of the ductus epididymis to one another and carries blood vessels and nerves. - Functionally, the epididymis is the site of sperm maturation, the process by which sperm acquire motility and the ability to fertilize an ovum. This occurs over a period of about 14 days. --> The epididymis also stores sperm and during sexual arousal helps propel sperm into the ductus (vas) deferens by peristaltic contraction of its smooth muscle. Sperm may remain in storage in the epididymis for up to several months. Any stored sperm that are not ejaculated by that time are eventually phagocytized and reabsorbed.

Spermiogenesis

- The final stage of spermatogenesis, spermiogenesis, is the maturation of haploid spermatids into sperm. - Because no cell division occurs in spermiogenesis, each spermatid develops into a single sperm cell. - During this process, spherical spermatids transform into elongated, slender sperm. An acrosome (described shortly) forms atop the condensing and elongating nucleus, a flagellum develops, and mitochondria multiply. Sustentacular cells dispose of the excess cytoplasm that is sloughed off during this process. - Finally, sperm are released from their connections to sustentacular cells, an event known as spermiation. - Sperm then enter the lumen of the seminiferous tubule. Fluid secreted by sustentacular cells pushes sperm along their way, toward the ducts of the testes. At this point, sperm are not yet able to swim.

Periodic abstinence

- The first physiologically based method, developed in the 1930s, is known as the rhythm method. It involves abstaining from sexual activity on the days that ovulation is likely to occur in each reproductive cycle. During this time (3 days before ovulation, the day of ovulation, and 3 days after ovulation) the couple abstains from intercourse. The effectiveness of the rhythm method for birth control is poor in many women due to the irregularity of the female reproductive cycle. - Another system is the sympto‐thermal method (STM), a natural, fertility‐awareness-based method of family planning that is used to either avoid or achieve pregnancy. STM utilizes normally fluctuating physiological markers to determine ovulation such as increased basal body temperature and the production of abundant, clear, stretchy cervical mucus that resembles uncooked egg white. These indicators, reflecting the hormonal changes that govern female fertility, provide a double‐check system by which a female knows when she is or is not fertile. Sexual intercourse is avoided during the fertile time to avoid pregnancy. STM users observe and chart these changes and interpret them according to precise rules.

Oogenisis

- The formation of gametes in the ovaries is termed oogenesis. Unlike spermatogenesis, which begins in males at puberty, oogenesis begins in females before they are born. As in spermatogenesis, meiosis takes place and the resulting germ cells undergo maturation. - During early fetal development, primordial (primitive) germ cells migrate from the yolk sac to the ovaries. There, germ cells differentiate within the ovaries into oogonia. - Oogonia are diploid (2n) stem cells that divide mitotically to produce millions of germ cells. Even before birth, most of these germ cells degenerate in a process known as atresia. However, a few develop into larger cells called primary oocytes

Endometrium

- The inner layer of the uterus, the endometrium, is highly vascularized and has three components: (1) An innermost layer composed of simple columnar epithelium (ciliated and secretory cells) lines the lumen. (2) An underlying endometrial stroma is a very thick region of lamina propria. (3) Endometrial (uterine) glands develop as invaginations of the luminal epithelium and extend almost to the myometrium. - The endometrium is divided into two layers. The stratum functionalis lines the uterine cavity and sloughs off during menstruation as a result of declining levels of progesterone from the ovaries. - The deeper layer, the stratum basalis, is permanent and gives rise to a new stratum functionalis after each menstruation. - Branches of the internal iliac artery called uterine arteries supply blood to the uterus. - Uterine arteries give off branches called arcuate arteries that are arranged in a circular fashion in the myometrium. - These arteries branch into radial arteries that penetrate deeply into the myometrium. Just before the branches enter the endometrium, they divide into two kinds of arterioles: Straight arterioles supply the stratum basalis with the materials needed to regenerate the stratum functionalis; spiral arterioles supply the stratum functionalis and change markedly during the menstrual cycle. - Blood leaving the uterus is drained by the uterine veins into the internal iliac veins. - The secretory cells of the mucosa of the cervix produce a secretion called cervical mucus, a mixture of water, glycoproteins, lipids, enzymes, and inorganic salts. - Cervical mucus is more hospitable to sperm at or near the time of ovulation because it is then less viscous and more alkaline. - At other times, a more viscous mucus forms a cervical plug that physically impedes sperm penetration. - Cervical mucus supplements the energy needs of sperm, and both the cervix and cervical mucus protect sperm from phagocytes and the hostile environment of the vagina and uterus. They may also play a role in capacitation, a functional change that sperm undergo in the female reproductive tract before they are able to fertilize a secondary oocyte. Capacitation causes a sperm cell's tail to beat even more vigorously and it prepares the sperm cell's plasma membrane to fuse with the oocyte's plasma membrane.

The menstrual phase

- The menstrual phase, also called menstruation or menses, lasts for roughly the first 5 days of the cycle. - Follicular fluid, secreted by the granulosa cells and filtered from blood in the capillaries of the theca folliculi, accumulates in the enlarging antrum while the oocyte remains near the edge of the follicle. - Menstrual flow from the uterus consists of 50-150 mL of blood, tissue fluid, mucus, and epithelial cells shed from the endometrium. --> This discharge occurs because the declining level of ovarian progesterone and estrogens stimulates release of prosta glandins that cause the uterine spiral arterioles to constrict. As a result, the cells they supply become oxygen‐deprived and start to die. - The preovulatory phase is the time between the end of menstruation and ovulation. --> The preovulatory phase of the cycle is more variable in length than the other phases and accounts for most of the difference when cycles are shorter or longer than 28 days. It lasts from days 6 to 13 in a 28‐day cycle. - By about day 6, a single secondary follicle in one of the two ovaries has outgrown all the others to become the dominant follicle. - Estrogens and inhibin secreted by the dominant follicle decrease the secretion of FSH, which causes other, less well‐developed follicles to stop growing and to degenerate. - Fraternal (nonidentical) twins or triplets result when two or three secondary follicles become codominant and later are ovulated and fertilized at about the same time. - Normally, the one dominant secondary follicle becomes the mature (graafian) follicle, which continues to enlarge until it is more than 20 mm in diameter and ready for ovulation. - With reference to the ovarian cycle, the menstrual and preovulatory phases together are termed the follicular phase because ovarian follicles are growing and developing. - Estrogens liberated into the blood by growing ovarian follicles stimulate the repair of the endometrium; cells of the stratum basalis undergo mitosis and produce a new stratum functionalis. - As the endometrium thickens, the short, straight endometrial glands develop, and the arterioles coil and lengthen as they penetrate the stratum functionalis. - The preovulatory phase is also referred to as the proliferative phase of the uterine cycle because the endometrium is proliferating.

Postovulatory phase

- The postovulatory phase of the female reproductive cycle is the time between ovulation and onset of the next menses. In duration, it is the most constant part of the female reproductive cycle. It lasts for 14 days in a 28‐day cycle, from day 15 to day 28. - The observation that three conditions—disordered eating, amenorrhea, and osteoporosis—often occur together in female athletes led researchers to coin the term female athlete triad. - Amenorrhea is the absence of menstruation. The most common causes of amenorrhea are pregnancy and menopause. In female athletes, amenorrhea results from reduced secretion of gonadotropin‐releasing hormone, which decreases the release of LH and FSH. --> As a result, ovarian follicles fail to develop, ovulation does not occur, synthesis of estrogens and progesterone wanes, and monthly menstrual bleeding ceases. Most cases of the female athlete triad occur in young women with very low amounts of body fat. Low levels of the hormone leptin, secreted by adipose cells, may be a contributing factor. - After ovulation, the mature follicle collapses, and the basement membrane between the granulosa cells and theca interna breaks down. Once a blood clot forms from minor bleeding of the ruptured follicle, the follicle becomes the corpus hemorrhagicum. - Theca interna cells mix with the granulosa cells as they all become transformed into corpus luteum cells under the influence of LH. Stimulated by LH, the corpus luteum secretes progesterone, estrogens, relaxin, and inhibin. The luteal cells also absorb the blood clot. - If the oocyte is not fertilized, the corpus luteum has a lifespan of only 2 weeks. At the end of this time period, its secretory activity declines, and it degenerates into a corpus albicans. - If the secondary oocyte is fertilized and begins to divide, the corpus luteum persists past its normal 2‐week life span. It is "rescued" from degeneration by human chorionic gonadotropin (hCG). - The presence of hCG in maternal blood or urine is an indicator of pregnancy and is the hormone detected by home pregnancy tests. - Because of the secretory activity of the endometrial glands, which begin to secrete glycogen, this period is called the secretory phase of the uterine cycle. - These preparatory changes peak about one week after ovulation, at the time a blastocyst might arrive in the uterus. - If fertilization does not occur, the levels of progesterone and estrogens decline due to degeneration of the corpus luteum. Withdrawal of progesterone and estrogens causes menstruation.

Prostate

- The prostate slowly increases in size from birth to puberty, and then expands rapidly. The size attained by age 30 typically remains stable until about age 45, when further enlargement may occur, constricting the urethra and interfering with urine flow. - The prostate is a single, doughnut‐shaped gland about the size of a ping‐pong ball. - The prostate secretes a milky, slightly acidic fluid (pH about 6.5) that contains several substances: 1. Citric acid in prostatic fluid is used by sperm for ATP production. 2. Several proteolytic enzymes, such as prostate‐specific antigen (PSA), pepsinogen, lysozyme, amylase, and hyaluronidase, eventually break down the clotting proteins from the seminal vesicles. 3. The function of the acid phosphatase secreted by the prostate is unknown. 4. Seminalplasmin in prostatic fluid is an antibiotic that can destroy bacteria. Seminalplasmin may help decrease the number of naturally occurring bacteria in semen and in the lower female reproductive tract.

Spermatic cord

- The spermatic cord is a supporting structure of the male reproductive system that ascends out of the scrotum. - . The spermatic cord and ilioinguinal nerve pass through the inguinal canal, an oblique passageway in the anterior abdominal wall just superior and parallel to the medial half of the inguinal ligament. - The canal, which is about 4-5 cm (about 2 in.) long, originates at the deep (abdominal) inguinal ring, a slitlike opening in the aponeurosis of the transversus abdominis muscle; the canal ends at the superficial (subcutaneous) inguinal ring, a somewhat triangular opening in the aponeurosis of the external oblique muscle. - In females, the round ligament of the uterus and ilioinguinal nerve pass through the inguinal canal. - The term varicocele refers to a swelling in the scrotum due to varicosities in the veins that drain the testes. It usually disappears when the person lies down, and typically does not require treatment.

Scrotum

- The supporting structure for the testes, consists of loose skin and an underlying subcutaneous layer that hangs from the root (attached portion) of the penis. - Externally, the scrotum looks like a single pouch of skin separated into lateral portions by a median ridge called the raphe. - Internally, the scrotal septum divides the scrotum into two compartments, each containing a single testis. - The septum is made up of a subcutaneous layer and muscle tissue called the dartos muscle, which is composed of bundles of smooth muscle fibers. The dartos muscle is also found in the subcutaneous layer of the scrotum. - Associated with each testis in the scrotum is the cremaster muscle. The cremaster muscle consists of a series of small bands of skeletal muscle that descend, as an extension of the internal oblique muscle, through the spermatic cord to surround the testis. - The scrotal nerves arise from the pudendal nerves, posterior cutaneous nerves of the thigh, and ilioinguinal nerves.

The vulva

- The term vulva, or pudendum, refers to the external genitals of the female. - The following are the components of the vulva: • Anterior to the vaginal and urethral openings is the mons pubis, an elevation of adipose tissue covered by skin and coarse pubic hair that cushions the pubic symphysis. • From the mons pubis, two longitudinal folds of skin, the labia majora, extend inferiorly and posteriorly. The labia majora are covered by pubic hair and contain an abundance of adipose tissue, sebaceous (oil) glands, and apocrine sudoriferous (sweat) glands. • Medial to the labia majora are two smaller folds of skin called the labia minora. Unlike the labia majora, the labia minora are devoid of pubic hair and fat and have few sudoriferous glands, but they do contain many sebaceous glands, which produce antimicrobial substances and provide some lubrication during intercourse. The labia minora are homologous to the spongy (penile) urethra. •The clitoris is a small cylindrical mass of erectile tissue and nerves located at the anterior junction of the labia minora. A layer of skin called the prepuce of the clitoris is formed at the point where the labia minora unite and covers the body of the clitoris. The body of the clitoris has two bodies of erectile tissue, the corpora cavernosa. Like the similar bodies in the male penis, the corpora cavernosa bend posteriorly to attach to the rami of the pubis and ischium as the crura of the clitoris. The exposed portion of the clitoris is the glans clitoris. The glans clitoris is homologous to the glans penis in males. Like the male structure, the clitoris is capable of enlargement upon tactile stimulation and has a role in sexual excitement in the female. • The region between the labia minora is the Vestibule. Within the vestibule are the hymen, the vaginal orifice, the external urethral orifice, and the openings of the ducts of several glands. The vestibule is homologous to the intermediate urethra of males. The vaginal orifice, the opening of the vagina to the exterior, occupies the greater portion of the vestibule and is bordered by the hymen. Anterior to the vaginal orifice and posterior to the clitoris is the external urethral orifice, the opening of the urethra to the exterior. On either side of the external urethral orifice are the openings of the ducts of the paraurethral glands or Skene's glands. These mucus‐secreting glands are embedded in the wall of the urethra. The paraurethral glands are homologous to the prostate. On either side of the vaginal orifice itself are the greater vestibular glands or Bartholin's glands, which open by ducts into a groove between the hymen and labia minora. They produce a small quantity of mucus during sexual arousal and intercourse that adds to cervical mucus and provides lubrication. The greater vestibular glands are homologous to the bulbourethral glands in males. Several lesser vestibular glands also open into the vestibule. • The bulb of the vestibule consists of two elongated masses of erectile tissue just deep to the labia on either side of the vaginal orifice. The bulb of the vestibule becomes engorged with blood during sexual arousal, narrowing the vaginal orifice and placing pressure on the penis during intercourse. The bulb of the vestibule is homologous to the corpus spongiosum and bulb of the penis in males.

Organs of male reproductive system

- The testes (male gonads), a system of ducts (including the epididymis, ductus deferens, ejaculatory ducts, and urethra), accessory sex glands (seminal vesicles, prostate, and bulbourethral glands), and several supporting structures, including the scrotum and the penis. - The testes produce sperm and secrete hormones. - The duct system transports and stores sperm, assists in their maturation, and conveys them to the exterior. - Semen contains sperm plus the secretions provided by the accessory sex glands. - The supporting structures have various functions. - The penis delivers sperm into the female reproductive tract and the scrotum supports the testes.