THE REPRODUCTIVE SYSTEM

1. CHAPTER # 27(b) THE REPRODUCTIVE SYSTEM

2. Hormonal Regulation of Male Reproductive Function • A sequence of hormonal regulatory events involving the hypothalamus, anterior pituitary gland, and the testes • The hypothalamic-pituitary-gonadal (HPG) axis

3. 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

4. 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)

5. 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

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

7. 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

8. 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

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

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

11. 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

12. 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

13. 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

14. 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

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

16. 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

17. 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

18. 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

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

20. 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

21. 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

22. 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

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

24. Uterus • Cervix: narrow neck, or outlet; projects into the vagina • Cervical canal communicates with the • Vagina via the external os • Uterine body via the internal os • Cervical glands secrete mucus that blocks sperm entry except during midcycle

25. Supports of the Uterus • Mesometrium—lateral support: portion of the broad ligament • Lateral cervical (cardinal) ligaments: from the cervix and superior part of the vagina to the walls of the pelvis • Uterosacral ligaments secure uterus to the sacrum • Round ligaments bind to the anterior wall

26. 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

27. Peritoneal Pouches • Sacs of peritoneum exist around the uterus • Vesicouterine pouch is between bladder and uterus • Rectouterine pouch is between rectum and uterus

28. Uterine Wall • Three layers • Perimetrium: serous layer (visceral peritoneum) • Myometrium: interlacing layers of smooth muscle • Endometrium: mucosal lining

29. Endometrium • Stratum functionalis (functional layer) • Changes in response to ovarian hormone cycles • Is shed during menstruation • Stratum basalis (basal layer) • Forms new functionalis after menstruation • Unresponsive to ovarian hormones

30. Uterine Vascular Supply • Uterine arteries: arise from internal iliacs • Arcuate arteries: in the myometrium • Radial branches in the endometrium branch into • Spiral arteries  stratum functionalis • Straight arteries  stratum basalis • Spasms of spiral arteries leads to shedding of stratum functionalis

31. Lumen of uterus Epithelium Capillaries Uterine glands Venous sinusoids Lamina propria of connective tissue Spiral (coiled) artery Straight artery Endometrial vein Smooth muscle fibers Radial artery Arcuate artery Uterine artery (b) Figure 27.13b

32. Vagina • Birth canal and organ of copulation • Extends between the bladder and the rectum from the cervix to the exterior • Urethra embedded in the anterior wall

33. Vagina • Layers of wall • Fibroelastic adventitia • Smooth muscle muscularis • Stratified squamous mucosa with rugae • Mucosa near the vaginal orifice forms an incomplete partition called the hymen • Vaginal fornix: upper end of the vagina surrounding the cervix

34. Mons pubis Labia majora Prepuce of clitoris Labia minora Clitoris (glans) Urethral orifice Vestibule Hymen (ruptured) Vaginal orifice Anus Opening of the duct of the greater vestibular gland (a) Figure 27.14a

35. External Genitalia (Vulva or Pudendum) • Mons pubis: fatty area overlying pubic symphysis • Labia majora: hair-covered, fatty skin folds • Labia minora: skin folds lying within labia majora • Vestibule: recess between labia minora

36. External Genitalia • Greater vestibular glands • Homologous to the bulbourethral glands • Release mucus into the vestibule for lubrication

37. External Genitalia • Clitoris • Erectile tissue hooded by a prepuce • Glans clitoris: exposed portion • Perineum • Diamond-shaped region between the pubic arch and coccyx • Bordered by the ischial tuberosities laterally

38. Clitoris Labia minora Labia majora Inferior ramus of pubis Pubic symphysis Anus Body of clitoris, containing corpora cavernosa Clitoris (glans) Crus of clitoris Urethral orifice Vaginal orifice Greater vestibular gland Bulb of vestibule (b) Fourchette Figure 27.14b

39. Mammary Glands • Modified sweat glands consisting of 15–25 lobes • Areola: pigmented skin surrounding the nipple • Suspensory ligaments: attach the breast to underlying muscle • Lobules within lobes contain glandular alveoli that produce milk

40. Mammary Glands • Milk  lactiferous ducts  lactiferous sinuses  open to the outside at the nipple

41. First rib Skin (cut) Pectoralis major muscle Suspensory ligament Adipose tissue Lobe Areola Nipple Opening of lactiferous duct Lactiferous sinus Lactiferous duct Lobule containing alveoli Hypodermis (superficial fascia) Intercostal muscles (a) (b) Figure 27.15

42. Breast Cancer • Usually arises from the epithelial cells of small ducts • Risk factors include: • Early onset of menstruation and late menopause • No pregnancies or first pregnancy late in life • Family history of breast cancer • 10% are due to hereditary defects, including mutations to the genes BRCA1 and BRCA2

43. Breast Cancer: Detection and Treatment • 70% of women with breast cancer have no known risk factors • Early detection via self-examination and mammography • Treatment depends upon the characteristics of the lesion: • Radiation, chemotherapy, and surgery followed by irradiation and chemotherapy

44. (a) Mammogram procedure Malignancy (b) Film of normal breast (c) Film of breast with tumor Figure 27.16

45. Oogenesis • Production of female gametes • Begins in the fetal period • Oogonia (2n ovarian stem cells) multiply by mitosis and store nutrients • Primary oocytes develop in primordial follicles • Primary oocytes begin meiosis but stall in prophase I

46. Oogenesis • Each month after puberty, a few primary oocytes are activated • One is selected each month to resume meiosis I • Result is two haploid cells • Secondary oocyte • First polar body

47. Oogenesis • The secondary oocyte arrests in metaphase II and is ovulated • If penetrated by sperm the second oocyte completes meiosis II, yielding • Ovum (the functional gamete) • Second polar body

48. Meiotic events Follicle development in ovary Before birth Oogonium (stem cell) Follicle cells Mitosis Oocyte Primary oocyte Primordial follicle Growth Infancy and childhood (ovary inactive) Primary oocyte (arrested in prophase I; present at birth) Primordial follicle Each month from puberty to menopause Primary follicle Primary oocyte (still arrested in prophase I) Secondary follicle Spindle Vesicular (Graafian) follicle Meiosis I (completed by one primary oocyte each month in response to LH surge) Secondary oocyte (arrested in metaphase II) First polar body Ovulation Sperm Meiosis II of polar body (may or may not occur) Ovulated secondary oocyte Meiosis II completed (only if sperm penetration occurs) In absence of fertilization, ruptured follicle becomes a corpus luteum and ultimately degenerates. Polar bodies (all polar bodies degenerate) Second polar body Ovum Degenating corpus luteum Figure 27.17

49. Ovarian Cycle • Monthly series of events associated with the maturation of an egg • Two consecutive phases (in a 28-day cycle) • Follicular phase: period of follicle growth (days 1–14) • Ovulation occurs midcycle • Luteal phase: period of corpus luteum activity (days 14–28)

50. Follicular Phase • Primordial follicle becomes primary follicle • The primordial follicle is activated • Squamouslike cells become cuboidal • Follicle enlarges to become a primary (1) follicle