Chapter 24 The Reproductive System Student Notes
I. The Male Reproductive System (pp. 672–683, Figs. 24.1–24.9).
A. The function of the male and the female reproductive systems is to produce offspring; primary sex organs, the gonads, produce gametes: the sperm in males, and the egg in females (p. 672 and Figs. 24.1 and 24.10).
B. All other genitalia in both sexes are accessory sex organs (p. 672).
C. The scrotum is an external sac of skin that contains the testes (pp. 672–673, Fig. 24.2).
D. The testes are the male primary sex organs or gonads and site of sperm production (pp. 673–674, Fig. 24.3).
1. Gross anatomical examination of a testis reveals the size is about 2.5 cm (1 inch) in width and 4 cm in length; the tunica vaginalis partially encloses each testis (pp. 673–674, Fig. 24.3).
2. Seminiferous tubules are the sperm-forming tubules; spermatogenesis is the process of forming sperm cells (pp. 674–677, Figs. 24.3–24.5).
i. Spermatogenic cells are spermatogonia, primary and secondary spermatocytes, and spermatids (p. 675, Fig. 24.3).
ii. Successive stages of spermatogenesis are (1) formation of spermatocytes, (2) meiosis, and (3) spermiogenesis (p. 675, Figs. 24.4–24.5).
iii. Sustentacular cells surround spermatogenic cells and form the blood-testis barrier (pp. 675–677).
iv. Myoid cells surround seminiferous tubules and help squeeze sperm through the tubules (p. 677, Fig. 24.3b).
v. Interstitial cells secrete androgens, primarily testosterone (p. 677, Fig. 24.3b).
E. The reproductive duct system in males traces the pathway sperm cells follow beginning with the seminiferous tubules and ending with the urethra (pp. 677–680, Figs. 24.6–24.8).
1. The epididymis is the site where sperm mature (p. 678, Fig. 24.6).
2. The ductus deferens stores and transports sperm during ejaculation (pp. 678–679, Figs. 24.1 and 24.6).
3. The spermatic cord contains the ductus deferens, blood vessels, and nerves; the inferior part lies in the scrotum and the superior part runs through the inguinal canal (pp. 679–680, Fig. 24.7).
4. The urethra carries sperm from the ejaculatory duct to outside the body (p. 680, Fig. 24.8).
F. Accessory glands in males include the seminal vesicles, the prostate gland, and the bulbourethral glands; accessory glands produce secretions that contribute to semen formation (pp. 680–683, Figs. 24.1 and 24.8–24.9).
1. The paired seminal vesicles secrete a sugar-rich fluid that forms 60% of the ejaculate (p. 680, Figs. 24.1 and 24.8).
2. The prostate gland surrounds the prostatic urethra; its secretions constitute about one third of the volume of semen and function to clot and liquefy ejaculated semen (pp. 680–681, Figs. 24.8–24.9).
3. The bulbourethral glands produce mucus that lubricates the urethra for sperm passage (p. 681, Figs. 24.1 and 24.8).
G. The penis is the male organ of intercourse and delivers sperm into the female reproductive tract (pp. 681–683, Figs. 24.1–24.8).
H. The male perineum contains the scrotum, the root of the penis, and the anus; the bony landmarks are the coccyx, the ischial tuberosities, and the pubic symphysis (p. 683 and Fig. 26.13a on page 744).
II. The Female Reproductive System (pp. 684–695, Figs. 24.10–24.22).
A. The female reproductive system differs from the male system in several important ways; the gametes are eggs, female organs prepare to support developing offspring, and female organs undergo changes according to the reproductive cycle called the menstrual cycle (p. 684, Figs. 24.10 and 24.19).
B. The ovaries are the female primary sex organs and the site of egg cell production (pp. 684–689, Figs. 24.11–24.12).
1. The ovarian cycle is the monthly menstrual cycle as it relates to the ovary; the ovarian cycle has three phases (1) the follicular phase, (2) ovulation, and (3) the luteal phase (pp. 685–688, Figs. 24.13–24.14).
i. During the follicular phase (first half of the ovarian cycle, days 1–14), 6–12 primordial follicles start to grow (pp. 685–687, Fig. 24.13).
ii. Ovulation is midpoint of the ovarian cycle; an oocyte is released from a follicle at the surface of the ovary (p. 687, Fig. 24.14).
iii. In the luteal phase (second half of the ovarian cycle, days 15–28), the ruptured follicle becomes the corpus luteum (pp. 687–688, Fig. 24.13).
2. Oogenesis, the production of female gametes, starts before birth and takes decades to complete (pp. 688–689, Fig. 24.15).
C. The uterine tubes (also called fallopian tubes or oviducts) receive the ovulated oocyte and provide a site for fertilization (p. 689, Figs. 24.11 and 24.16).
D. The uterus (womb) is a hollow, thick-walled organ whose functions are to receive, retain, and nourish a fertilized egg throughout pregnancy (pp. 690–693, Figs. 24.11 and 24.17–24.19).
1. Supports of the uterus are several ligaments, mesenteries, and muscles of the pelvic floor (pp. 690–691, Figs. 24.11 and 24.17).
2. The uterine wall is composed of three basic layers: an outer perimetrium, a middle myometrium, and an inner endometrium (pp. 691–693, Figs. 24.11 and 24.18).
3. The uterine cycle is the menstrual cycle as it involves the endometrium (p. 693, Fig. 24.19).
E. The vagina is the distensible, muscular tube that connects the uterus to the body’s exterior; it receives the penis and semen during intercourse and acts as the birth canal (p. 693, Fig. 24.10).
F. The external genitalia, also called the vulva, are the female reproductive structures that lie external to the vagina in the diamond-shaped perineum (pp. 693–694, Figs. 24.20–24.21).
G. The mammary glands are modified sweat glands that are present in both sexes but function only in lactating females (pp. 694–695, Fig. 24.22).
III. Pregnancy and Childbirth (pp. 695–701, Figs. 24.23–24.26).
A. Pregnancy begins with a fertilized oocyte and ends with production of offspring nine months later (p. 695).
1. Events leading to fertilization are the acrosomal and cortical reactions that accomplish the sperm penetration of an oocyte (pp. 695–697, Fig. 24.23).
2. Implantation occurs in the uterus about six days after fertilization (p. 697, Figs. 24.25–24.25).
3. Formation of the placenta involves both embryonic (trophoblastic) and maternal (endometrial) tissues (pp. 697–699, Fig. 24.25).
4. Anatomy of the placenta ensures no mixing of maternal and fetal blood occurs; the placenta is an organ of transport between the mother and fetus (pp. 699–700, Fig. 24.25).
B. Childbirth or parturition, the act of giving birth, occurs an average of 266 days after fertilization and 280 days after the last menstrual period; the stages of labor include dilation, expulsion, and the placental stage (pp. 700–701, Fig. 24.26).
IV. Disorders of the Reproductive System (pp. 701–702).
A. Cancers are the primary cause of disorders of the male and female reproductive systems (p. 701).
B. Reproductive system cancers in males include testicular cancer and prostate cancer (p. 701).
1. Testicular cancer affects approximately 1 of 50,000 males most often in the age bracket of 15-35 years; this cancer is cured in 95% of all cases (p. 701).
2. Prostate cancer is a slow-growing cancer that is the second most common cause of cancer death in men; lung cancer is first (p. 701).
C. Reproductive cancers in females include ovarian cancer, endometrial cancer, cervical cancer, and breast cancer (pp. 701–702).
1. Ovarian cancer affects 1.4% of women and is the fifth most common cause of cancer death in women (pp. 701–702).
2. Endometrial cancer affects 2% of women and is the fourth most common cause of death in women (after lung, breast, and colorectal cancers) (p. 702).
3. Cervical cancer occurs in 1% of women between ages 30-50 years; survival rates improve with early detection (p. 702).
4. Breast cancer, the second most common cause of cancer deaths in women, kills 3% of the women in the United States (p. 702).
V. The Reproductive System Throughout Life (pp. 702–706, Figs. 24.27–24.29).
A. Embryonic development of the sex organs of both males and females begin development during week 5 (pp. 702–705, Figs. 24.27–24.28).
B. Descent of the gonads occurs in both sexes after forming in the dorsal abdomen; testes descend into the scrotum and ovaries descend into the pelvis (p. 705, Fig. 24.29).
C. Puberty generally occurs between ages 10 and 15 when reproductive organs mature and reproduction is possible (p. 706).
D. Menopause in women occurs normally between ages 46 and 54 and marks the end of ovulation and menstruation (p. 706).