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1. 27 The Reproductive System: Part A

2. Reproductive System • Primary sex organs (gonads): testes and ovaries • Produce sex cells (gametes) • Secrete steroid sex hormones • Androgens (males) • Estrogens and progesterone (females) • Accessory reproductive organs: ducts, glands, and external genitalia

3. Reproductive System • Sex hormones play roles in • Development and function of the reproductive organs • Sexual behavior and drives • Growth and development of many other organs and tissues

4. Male Reproductive System • Testes (within the scrotum) produce sperm • Sperm are delivered to the exterior through a system of ducts • Epididymis  vas deferens  ejaculatory duct  urethra

5. Male Reproductive System • Accessory sex glands: seminal vesicles, prostate, and bulbourethral glands • Empty secretions into the ducts during ejaculation

6. Ureter Urinary bladder Prostatic urethra Peritoneum Membranous urethra Seminal vesicle Ampulla of ductus deferens Urogenital diaphragm Pubis Ejaculatory duct Corpus cavernosum Corpus spongiosum Rectum Prostate Bulbourethral gland Epididymis Glans penis Anus Prepuce Bulb of penis Testis Ductus (vas) deferens External urethral orifice Scrotum Figure 27.1

7. The Scrotum • Sac of skin and superficial fascia • Hangs outside the abdominopelvic cavity • Contains paired testes • 3C lower than core body temperature (temperature necessary for sperm production) • Sperm would die/be malformed at internal body temperature

8. The Scrotum • Temperature is kept constant by two sets of muscles • Smooth muscle that wrinkles scrotal skin (dartos muscle) • Bands of skeletal muscle that elevate the testes (cremaster muscles)

9. Urinary bladder Superficial inguinal ring (end of inguinal canal) Testicular artery Ductus (vas) deferens Spermatic cord Penis Autonomic nerve fibers Middle septum of scrotum Pampiniform venous plexus Cremaster muscle Epididymis External spermatic fascia Tunica vaginalis (from peritoneum) Superficial fascia containing dartos muscle Tunica albuginea of testis Scrotum Internal spermatic fascia Skin Figure 27.2

10. The Testes • Each is surrounded by two tunics • Tunica vaginalis, derived from peritoneum • Tunica albuginea, the fibrous capsule • Septa extend inward and form ~250 lobules • Each contains 4 seminiferous tubules, which produce sperm

11. Spermatic cord Blood vessels and nerves Ductus (vas) deferens Testis Head of epididymis Seminiferous tubule Efferent ductule Rete testis Lobule Straight tubule Septum Tunica albuginea Body of epididymis Tunica vaginalis Duct of epididymis Cavity of tunica vaginalis Tail of epididymis (a) Figure 27.3a

12. The Penis • Spongy urethra and three cylindrical bodies of erectile tissue (spongy network of connective tissue and smooth muscle with vascular spaces) • Corpus spongiosum surrounds the urethra and expands to form the glans and bulb • Corpora cavernosa are paired dorsal erectile bodies • Erection: erectile tissue fills with blood, causing the penis to enlarge and become rigid

13. Ureter Ampulla of ductus deferens Seminal vesicle Urinary bladder Ejaculatory duct Prostate Prostatic urethra Bulbourethral gland and duct Orifices of prostatic ducts Membranous urethra Urogenital diaphragm Bulb of penis Root of penis Crus of penis Bulbourethral duct opening Ductus deferens Corpora cavernosa Epididymis Corpus spongiosum Shaft (body) of penis Testis Section of (b) Spongy urethra Glans penis Prepuce (foreskin) (a) External urethral orifice Dorsal vessels and nerves Corpora cavernosa Urethra Skin Tunica albuginea of erectile bodies Deep arteries Corpus spongiosum (b) Figure 27.4

14. The Male Duct System • Epididymis • Vas deferens • Ejaculatory duct • Urethra

15. Epididymis • Head: contains the efferent ductules • Duct of the epididymis • Microvilli (stereocilia) absorb testicular fluid and pass nutrients to stored sperm • During ejaculation the epididymis contracts, expelling sperm into the vas deferens

16. Vas Deferens and Ejaculatory Duct • Vas deferens • Passes through the inguinal canal • Propels sperm from the epididymis to the urethra • Vasectomy: cutting and ligating the vas deferens, which is a nearly 100% effective form of birth control

17. Urethra • Conveys both urine and semen (at different times) • Has three regions • Prostatic urethra • Membranous urethra • Spongy (penile) urethra

18. Accessory Glands: Seminal Vesicles • Produces viscous alkaline seminal fluid • Fructose, ascorbic acid, coagulating enzyme (vesiculase), and prostaglandins • 70% of the volume of semen • Duct of seminal vesicle joins the vas deferens to form the ejaculatory duct

19. Accessory Glands: Prostate • Encircles part of the urethra inferior to the bladder • Secretes milky, slightly acid fluid: • Contains citrate, enzymes, and prostate-specific antigen (PSA) • Plays a role in the activation of sperm

20. Accessory Glands: Bulbourethral Glands (Cowper’s Glands) • Pea-sized glands inferior to the prostate • Prior to ejaculation, produce thick, clear mucus • Lubricates the glans penis • Neutralizes traces of acidic urine in the urethra

21. Ureter Urinary bladder Prostatic urethra Peritoneum Membranous urethra Seminal vesicle Ampulla of ductus deferens Urogenital diaphragm Pubis Ejaculatory duct Corpus cavernosum Corpus spongiosum Rectum Prostate Bulbourethral gland Epididymis Glans penis Anus Prepuce Bulb of penis Testis Ductus (vas) deferens External urethral orifice Scrotum Figure 27.1

22. Semen • Mixture of sperm and accessory gland secretions • Contains nutrients (fructose), protects and activates sperm, and facilitates their movement (e.g., relaxin) • Prostaglandins in semen • Decrease the viscosity of mucus in the cervix • Stimulate reverse peristalsis in the uterus

23. Semen • Alkalinity neutralizes the acid in the male urethra and female vagina • Antibiotic chemicals destroy certain bacteria • Clotting factors coagulate semen just after ejaculation, then fibrinolysin liquefies it

24. Male Sexual Response • Erection: • Parasympathetic reflex promotes release of nitric oxide (NO) • NO causes erectile tissue to fill with blood • Expansion of the corpora cavernosa • Compresses drainage veins and maintains engorgement • Corpus spongiosum keeps the urethra open • Impotence: the inability to attain erection

25. Male Sexual Response • Ejaculation • Propulsion of semen from the male duct system • Sympathetic spinal reflex causes • Ducts and accessory glands to contract and empty their contents • Bladder sphincter muscle to constrict, preventing the expulsion of urine • Bulbospongiosus muscles to undergo a rapid series of contractions

26. Mitosis of Spermatogenesis • Begins at puberty • Spermatogenesis • Stem cells in contact with the epithelial basal lamina • Each mitotic division  a type A daughter cell and a type B daughter cell

27. Basal lamina Type A daughter cell remains at basal lamina as a stem cell Spermatogonium (stem cell) Mitosis Type B daughter cell Growth Enters meiosis I and moves to adluminal compartment Primary spermatocyte Meiosis I completed Secondary spermatocytes Meiosis II Early spermatids Late spermatids Spermatozoa (b) Events of spermatogenesis, showing the relative position of various spermatogenic cells Figure 27.7b

28. Sperm • Major regions • Head: genetic region; nucleus and helmetlike acrosome containing hydrolytic enzymes that enable the sperm to penetrate an egg • Midpiece: metabolic region; mitochondria • Tail: locomotor region; flagellum

29. HPG Axis • Hypothalamus releases gonadotropin-releasing hormone (GnRH) • GnRH stimulates the anterior pituitary to secrete FSH and LH • FSH causes sustentacular cells to release androgen-binding protein (ABP), which makes spermatogenic cell receptive to testosterone • LH stimulates interstitial cells to release testosterone

30. HPG Axis • Testosterone is the final trigger for spermatogenesis • Feedback inhibition on the hypothalamus and pituitary results from • Rising levels of testosterone • Inhibin (released when sperm count is high)

31. 1 GnRH Anterior pituitary Via portal blood 8 7 2 Inhibin 2 LH FSH Interstitial cells 4 3 6 Testosterone Somatic and psychological effects at other body sites Sustentacular cell Spermatogenic cells 5 Seminiferous tubule Stimulates Inhibits Figure 27.9

32. Mechanism and Effects of Testosterone Activity • Testosterone • Synthesized from cholesterol (steroid hormone) • Transformed to exert its effects on some target cells • Dihydrotestosterone (DHT) in the prostate • Estrogen in some neurons in the brain

33. Mechanism and Effects of Testosterone Activity • Prompts spermatogenesis • Targets all accessory organs; deficiency leads to atrophy • Has multiple anabolic effects throughout the body • Is the basis of the sex drive (libido) in males

34. Male Secondary Sex Characteristics • Features induced in the nonreproductive organs by male sex hormones (mainly testosterone) • Appearance of pubic, axillary, and facial hair • Enhanced growth of the chest and deepening of the voice • Skin thickens and becomes oily • Bones grow and increase in density • Skeletal muscles increase in size and mass

35. Female Reproductive Anatomy

36. Female Reproductive Anatomy • Ovaries: female gonads • Produce female gametes (ova) • Secrete female sex hormones (estrogen and progesterone) • Accessory ducts include • Uterine tubes • Uterus • Vagina

37. Female Reproductive Anatomy • Internal genitalia • Ovaries • Uterine tubes • Uterus • Vagina • External genitalia • The external sex organs

38. Suspensory ligament of ovary Infundibulum Uterine tube Ovary Fimbriae Peritoneum Uterus Round ligament Uterosacral ligament Vesicouterine pouch Perimetrium Rectouterine pouch Urinary bladder Pubic symphysis Rectum Mons pubis Posterior fornix Cervix Urethra Anterior fornix Clitoris Vagina External urethral orifice Anus Hymen Urogenital diaphragm Labium minus Greater vestibular (Bartholin’s) gland Labium majus Figure 27.10

39. Ovaries • Held in place by several ligaments • Ovarian ligament: anchors ovary medially to the uterus • Suspensory ligament: anchors ovary laterally to the pelvic wall • Mesovarium: suspends the ovary • Broad ligament: supports the uterine tubes, uterus, and vagina; also contains the suspensory ligament and the mesovarium

40. Suspensory ligament of ovary Uterine (fallopian) tube Uterine tube Ovarian blood vessels Lumen (cavity) of uterus Fundus of uterus Ampulla Ovary Isthmus Mesosalpinx Infundibulum Mesovarium Broad ligament Fimbriae Mesometrium Round ligament of uterus Ovarian ligament Endometrium Body of uterus Wall of uterus Myometrium Ureter Perimetrium Uterine blood vessels Internal os Isthmus Cervical canal Uterosacral ligament Lateral cervical (cardinal) ligament External os Vagina Lateral fornix Cervix (a) Figure 27.12a

41. Ovaries • Blood supply: ovarian arteries and the ovarian branch of the uterine artery • Surrounded by a fibrous tunica albuginea • Two poorly defined regions • Cortex: ovarian follicles • Medulla: large blood vessels and nerves

42. Ovaries • Follicle • Immature egg (oocyte) surrounded by • Follicle cells (one cell layer thick) • Granulosa cells (when more than one layer is present)

43. Follicles • Several stages of development • Primordial follicle: squamouslike follicle cells + oocyte • Primary follicle: cuboidal or columnar follicle cells + oocyte • Secondary follicle: two or more layers of granulosa cells + oocyte • Late secondary follicle: contains fluid-filled space between granulosa cells; coalesces to form a central antrum

44. Ovaries • Vesicular (Graafian) follicle • Fluid-filled antrum forms; follicle bulges from ovary surface • Ovulation • Ejection of the oocyte from the ripening follicle • Corpus luteum develops from ruptured follicle after ovulation

45. Tunica albuginea Oocyte Granulosa cells Late secondary follicle Cortex Degenerating corpus luteum (corpus albicans) Mesovarium and blood vessels Germinal epithelium Vesicular (Graafian) follicle Primary follicles Antrum Oocyte Ovarian ligament Zona pellucida Theca folliculi Medulla Ovulated oocyte Corpus luteum Corona radiata Developing corpus luteum (a) Diagrammatic view of an ovary sectioned to reveal the follicles in its interior Figure 27.11a

46. Female Duct System • Uterine (fallopian) tubes or oviducts • Uterus • Vagina

47. Uterine Tubes • Ampulla • Distal expansion with infundibulum near ovary • Usual site of fertilization • Ciliated fibriae of infundibulum create currents to move oocyte into uterine tube • Isthmus: constricted region where tube joins uterus

48. Uterine Tubes • Oocyte is carried along by peristalsis and ciliary action • Nonciliated cells nourish the oocyte and the sperm • Mesosalpinx: mesentery that supports the uterine tubes

49. Suspensory ligament of ovary Uterine (fallopian) tube Uterine tube Ovarian blood vessels Lumen (cavity) of uterus Fundus of uterus Ampulla Ovary Isthmus Mesosalpinx Infundibulum Mesovarium Broad ligament Fimbriae Mesometrium Round ligament of uterus Ovarian ligament Endometrium Body of uterus Wall of uterus Myometrium Ureter Perimetrium Uterine blood vessels Internal os Isthmus Cervical canal Uterosacral ligament Lateral cervical (cardinal) ligament External os Vagina Lateral fornix Cervix (a) Figure 27.12a

50. Uterus • Body: major portion • Fundus: rounded superior region • Isthmus: narrowed inferior region