CHAPTER 28: Reproductive System
INTRODUCTION
* Definition: gametes & gonads
Gametes: germ cells, which organisms use to sexually reproduce.
Gonad: Reproductive organs (Testes in males and ovaries in females) that produce gametes and secrete sex hormones. * Define gynecology, urology & andrology
Gynecology: The branch of medicine that is concerned with the diagnosis and treatment of diseases of the female reproductive system.
Urology: The study of the urinary system, as well as the branch of medicine that deals with the diagnosis and treatment of the male reproductive system.
Andrology: The branch of medicine that deals with male disorders, like infertility and sexual dysfunction.
28.1 MALE REPRODUCTIVE SYSTEM * The male reproductive organs & the functions of the male reproductive system (Figure 28.1) * The male reproductive organs include: the testes1, a system of ducts2 (including the epididymis, ductus vas deferens, ejaculatory ducts, and urethra), accessory sex glands3 (seminal vesicles, prostate, and bulbourethral glands) and several supporting structures including the scrotum4 and penis5.
Functions:
1. The testes produce sperm and male sex hormone, testosterone. 2. The ducts transport, store and assist in maturation of sperm. 3. The accessory sex glands secrete most of the liquid portion of semen. 4. The penis contains the urethra, a passageway for ejaculation of semen and excretion of urine.

Major organs include: testes, ducts, accessory sex glands, the scrotum and the penis. * Scrotum: location and function of the scrotum & its muscle tissues * The scrotum supporting structure of the testes, hangs from the root of the penis. * There are two main muscle tissues, the dartos muscle1 that is composed of bundles of smooth muscle fibers. * The cremaster muscle2 series of small bands of skeletal muscle that descends as an extension of internal oblique muscle through the spermatic cord to surround the testes. * Testes A. Seminiferous tubules: (Figure 28.4). a) Spatial relationship: tunica vaginalis, tunica albuginea, lobules, seminiferous tubules b) Seminiferous tubules: location & function of 2 types of cells * The lobules contain the tightly coiled seminiferous tubules, where sperm are produced. * The seminiferous tubules contain 2 types of cells: Spermatogenic cells1 form the sperm cells, and are located near the basement membrane of the tubules.
Sertoli or Sustentacular cells2 support the spermatogenic cells in creating sperm, and are found around the spermatogenic cells, near the basement membrane. c) The blood-testis barrier: formation & function
The blood testis barrier is made of tight junctions between neighboring sertoli/sustentacular cells. These tight junctions act as a blood-testis barrier because substances first pass through sertoli cells before they can reach the developing sperm cells. d) Functions of sertoli cells
Sertoli (sustentacular) cells nourish developing sperm, phagocytize excess material, control the movement of spermatogenic cells and the release of sperm into the lumen of the seminiferous tubule.
They also produce fluid for sperm support, secret the hormone inhibin, and regulate the effects of testosterone and FSH (follicle-stimulating hormone). e) Location & function of the Leydig cells or interstitial cells (Figure 28.4) * In the spaces between adjacent seminiferous tubules are clusters of cells called leydig cells. These cells secrete testosterone (most prevalent androgen).

B. Spermatogenesis: a) How long does it take in human?
~65-75 days b) Begins as diploid spermatogonia (stem cells) ► 1) some remain as precursor stem cell, 2) others undergo mitosis for sperm production (Figure 28.5) ► final stage is the development of haploid sperm cells.

C. Sperm
Mature sperm consist of a head, midpiece, and tail (Figure 28.6). They are produced at the rate of about 300 million per day and, once ejaculated, have a life expectancy of 48 hours within the female reproductive tract. Their function is to fertilize a secondary oocyte.

D. Hormonal Control of the testicular function a) At puberty, gonadotropin releasing hormone stimulates anterior pituitary to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). (Figure 28.7 entire content)

b) Effects of inhibin & androgen including testosterone
Inhibin inhibits the secretion of follicle stimulating hormone (FSH), which helps to regulate the rate of sperm production.
Androgen-binding protein is stimulated by FSH, which binds to testosterone, which helps keeps the concentration high.
Testosterone is needed to complete the final steps of spermatogenesis. . c) Negative feedback systems regulate testosterone production (Figure 28.8)

* Reproductive System Ducts in Males A. Ducts of the testis
Straight tubules > Rete testis > efferent ducts > ductus epididymis B. Epididymis: location & function
The epididymis is located along the posterior border of each testis.
Ths is the site of sperm maturation, where sperm become able to fertilize and move freely. It also propels sperm into the ductus deferens when sexually aroused. C. Ductus Deferens: location & function
The ductus deferens (vas deferens) extends out of the ductus epididymis a) Spermatic cord: its contents (Figure 28.2).

D. Ejaculatory ducts: location & function (Figure 28.9).

E. Urethra: location & function
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. It passes through the prostate, the deep muscles of the perineum, and the penis, and is subdivided into three parts. * Accessory Sex Glands (Figure 28.9): functions of their secretions A. The seminal vesicles: function of fructose, prostaglandin & alkalinity of the fluid
Fructose is used by sperm for ATP production
Prostaglandins help with sperm health (motility, viability)
The alkalinity help keep the sperm intact when it enters the acidic vagina. B. The prostate gland: function of citric acid & proteolytic enzymes as a group
Citric acid is used in the Krebs cycle for ATP
The proteolytic enzymes help break down the clotting proteins the in seminal vesicles. C. The bulbourethral (Cowper’s) glands: secretion
Cowper’s glands secrete an alkaline fluid to protect the sperm when it passes through the urethra. * Semen (seminal fluid): a mixture of spermatozoa and accessory sex gland secretions that provides the fluid in which spermatozoa are transported, provides nutrients, and neutralizes the acidity of the male urethra and female vagina. * Penis
Erection: mechanism
Upon sexual stimulation, parasympathetic fibers from the sacral portion of the spinal cord produce and release nitric oxide (NO). The NO causes smooth muscle in the walls of arterioles supplying erectile tissue to relax, which allows these blood vessels to dilate. NO also causes the smooth muscle within the erectile tissue to relax, resulting in widening of the blood sinuses. The combination of increased blood flow and widening of the blood sinuses results in an erection.
Ejaculation: mechanism
Ejaculation 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, preventing urine from being expelled during ejaculation, and semen from entering the urinary bladder. Even before ejaculation occurs, peristaltic contractions in the epididymis, ductus (vas) deferens, seminal vesicles, ejaculatory ducts, and prostate propel semen into the penile portion of the urethra (spongy urethra). Typically, this leads to emission (eˉ-MISH-un), the discharge of a small volume of semen before ejaculation. Emission may also occur during sleep (nocturnal emission). The musculature of the penis (bulbospongiosus, ischiocavernosus, and superficial transverse perineal muscles), which is supplied by the pudendal nerve, also contracts at ejaculation.
28.2 FEMALE REPRODUCTION SYSTEM * Female organs of reproduction & functions of the female reproductive system (Figure 28.11)
Ovaries, the fallopian tubes, oviducts, the uterus, the vagina, vulva, and the mammary glands. * Ovaries A. The ovaries are paired glands that are homologous to the testes: produce gametes & hormones B. The histology of the ovary is illustrated in Figure 28.13. (following outline only) a) Ovarian follicles, in various degrees of development, lie in the cortex and contain oocytes at different stages of gametogenesis b) A mature (Graafian) follicle expels a secondary oocyte by a process called ovulation. c) A corpus luteum contains the remnants of an ovulated follicle and produces progesterone, estrogens, relaxin, and inhibin until it degenerates into a corpus albicans.

C. Oogenesis and follicular development (Table 28.1, entire content) a) Oogenesis a. occurs in the ovaries before birth, results in formation of primordial follicles containing primary oocytes b. each month after puberty, results in the formation of a mature follicle containing one 2ndary oocyte.

b) Define ovulation
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. c) Ovarian cysts (Clinical Connection)
Ovarian cysts are fluid-filled sacs in or on an ovary. Such cysts are relatively common, are usually noncancerous, and frequently disappear on their own. Cancerous cysts are more likely to occur in women over 40. Ovarian cysts may cause pain, pressure, a dull ache, or fullness in the abdomen; pain during sexual intercourse; delayed, painful, or irregular menstrual periods; abrupt onset of sharp pain in the lower abdomen; and/or vaginal bleeding. Most ovarian cysts require no treatment, but larger ones (more than 5 cm or 2 in.) may be removed surgically. * Uterine Tube A. The uterine (Fallopian) tubes: location & function (Figure 28.16)
The fallopian tubes extend laterally from the uterus, and provide a route for sperm to reach an ovum. B. Movement of a secondary oocyte toward the uterus

* Uterus A. The uterus (womb): function
The uterus 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 fertilized ovum, development of the fetus during pregnancy, and labor. During reproductive cycles when implantation does not occur, the uterus is the source of menstrual flow. B. Anatomical subdivisions
(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 C. Histology: 3 tissue layers & function
Perimetrium is the outer layer. It encases the uterus and covers the bladder anteriorly and the rectum posteriorly, creating pouches of tissue.
Myometrium is the middle layer, composed of three layers of smooth muscle (Thickest -> thinnest from fundus to cervix). During labor am childbirth, coordinated contractions occur to help expel the fetus from the uterus.
Endometrium The inner layer of the uterus is highly vascularized and has three components:
(1) An innermost layer composed of simple columnar epithelium lines the lumen.
(2) An underlying endometrial stroma is a very thick region of lamina propria. (Areolar tissue)
(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 (functional layer) lines the uterine cavity and sloughs off during menstruation. D. Cervical mucus: site of production & function
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 usually less viscous and more alkaline, providing a better environment for sperm to work, providing nutrients. Sometimes it becomes more viscous to slow down sperm penetration. E. Hysterectomy: definition (Clinical Connection)
Hysterectomy is the surgical removal of the uterus, is the most common gynecological operation. It may be indicated in conditions such as fibroids, which are noncancerous tumors composed of muscular and fibrous tissue; endometriosis; pelvic inflammatory disease; recurrent ovarian cysts; excessive uterine bleeding; and cancer of the cervix, uterus, or ovaries.

* Vagina A. Function
It is the receptacle for the penis during sexual intercourse, the outlet for menstrual flow, and the passageway for childbirth. (Such a formal definition…) B. Define vaginal rugae
Transverse folds of non-keratinized stratified squamous epithelium and areolar conncective tissue that lies in series. C. pH of the mucosal environment & function
Is acidic due to glycogen stores, and helps to stop microbial growth but can also harm sperm. * Vulva A. What does the term vulva, or pudendum, refer to? (Figure 28.20)
The vulva refers to the external genitals of females

B. Table 28.2: entire content

* Perineum: A. Define the area (Figure 28.21)
The perineum is the diamond-shaped area medial to the thighs and buttocks of both males and females.

B. Define episiotomy (Clinical Connection).
During childbirth, the emerging fetus normally stretches the perineal region. However, if it appears that the stretching could be excessive, a physician may elect to perform an episiotomy, a perineal cut between the vagina and anus made with surgical scissors to widen the birth canal. * Mammary Glands A. The mammary glands are modified sudoriferous (sweat) glands B. The essential functions of the mammary glands
Milk creation, secretion, and ejection
28.3 THE FEMALE REPRODUCTIVE CYCLE * The general term female reproductive cycle encompasses the ovarian and uterine cycles, the hormonal changes that regulate them, and cyclical changes in the breasts and the cervix. A. The ovarian cycle is a series of events associated with the maturation of an ovum. B. The uterine (menstrual) cycle involves changes in the endometrium to prepare for the reception of a fertilized ovum. C. Hormonal Regulation of the Female Reproductive Cycle: the menstrual and ovarian cycles are controlled by GnRH from the hypothalamus, which stimulates the release of FSH and LH by the anterior pituitary gland (Figure 28.23): functions of FSH & LH, estrogens, progesterone, relaxin & inhibin

* Phases of the Female Reproductive Cycle: may be divided into four phases (Figure 28.24) A. The menstrual phase (menstruation) lasts for approximately the first 5 days of the cycle. a) In ovaries (follicular phase): hormone influence & follicular development
Follicle stimulating hormone (FSH), develops primordial follicles into primary, and then primary into secondary follicles (over a course of months) b) In uterus: hormone influence & menses
Decrease levels of estrogen and progesterone triggers a release of prostaglandins. This cause uterine (spiral) arterioles to constrict, killing endometrial tissue. B. The preovulatory phase, lasting from days 6-13 in a 28-day cycle. a) In ovaries (follicular phase): follicular development & hormone secretion
Some secondary follicles start to secrete estrogen and inhibin to develop. One becomes the dominant follicle and secretes more. This decreases FSH levels. The dominant follicle continues growing until it is ready for ovulation. b) In uterus (proliferative phase): hormone influence & endometrial repair occurs.
Estrogens in the blood stimulate endometrial repair. C. Ovulation, usually occurs on 14th day of 28-day cycle a) Describe ovulation process
High levels of estrogen stimulate a release of gonadotropin releasing hormone (GnRH) from hypothalamus, which causes the anterior pituitary to release luteinizing hormone (LH) and FSH. LH stimulates the follicle, and causes the mature secondary oocyte (Graafian follicle) to release into the fallopian tube. b) Hormone influence: positive feedback effect of estrogen

D. The postovulatory phase, lasts from days 15-28 in a 28-day cycle a) In ovaries (luteal phase): development of corpus luteum & secretion of hormones * if fertilization and implantation do not occur: fate of corpus luteum & secretion of hormones
The oocyte’s secretory activity declines, and it degenerates into a corpus albicans. As the levels of progesterone, estrogens, and inhibin decrease, release of GnRH, FSH, and LH rises due to loss of negative feedback suppression by the ovarian hormones. Follicular growth resumes and a new ovarian cycle begins * If fertilization and implantation do occur: fate of corpus luteum & function of hCG
If the secondary oocyte isfertilized 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). This hormone produced by the chorion of the embryo begins about 8 days after fertilization. Like LH, hCG stimulates the secretory activity of the corpus luteum. The presence of hCG in maternal blood or urine is an indicator of pregnancy and is the hormone detected by home pregnancy tests b) In uterus (secretory phase): hormone influence & activity of the endometrial glands in anticipation of implantation. Progesterone and estrogens produced by the corpus luteum promote growth and coiling of the endometrial glands, vascularization of the superficial endometrium, and thickening of the endometrium. 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 1 week after ovulation, at the time a fertilized ovum 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. E. Figure 28.26 : entire content

28.4 BIRTH CONTROL METHODS AND ABORTION * Know all methods (bold) listed in 28.4 Birth control Methods and abortion
Vasectomy
Tubal litigation
Combined pill
Extended birth cycle birth control
Minipill
Contraceptive skin patch
Vaginal ring
Emergency contraception
Hormone injections
IUDs
Spermicides
Condoms
Diaphragm
Rhythm method
Sympto-thermal method
Abortion (aspiration and chemical)
28.6 AGING AND THE REPRODUCTIVE SYSTEMS * Puberty refers to the period of time when secondary sexual characteristics begin to develop and the potential for sexual reproduction is reached. * In females, the reproductive cycle normally occurs once each month from menarche, the first menses, to menopause, the last menses. * In males, declining reproduction function is more subtle, with males often retaining reproductive capacity into their 80s or 90s.
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Figure Questions: 28.1-4, 28.7-9, 28.10,-11, 28.13-18, 28.22-27