Human Anatomy, First Edition McKinley & O'Loughlin

1. Human Anatomy, First EditionMcKinley & O'Loughlin Chapter 28 : The Reproductive System

2. Reproductive Systems • Main function: propagation of the species • To achieve this goal: • Must ensure sexual maturation • Produce gametes (n). • Male and female structures are homologues: • derived from common developmental tissues

4. Homologous structures

5. Comparison of the Female and Male Reproductive Systems • Primary sex organs called gonads. • ovaries in females • testes in males • Produce gametes which unite to form a new individual. • oocytes • sperm • Gonads produce large amounts of sex hormones which affect maturation, development, and changes in the activity of the reproductive system organs. • estrogen and progesterone in the female • androgens (esp. testosterone) in the male

6. Comparison of the Female and Male Reproductive Systems • Both have accessory reproductive organs • duct systems • carry gametes away from the gonads • toward the site of fertilization in females • to the outside of the body in males • Fertilization occurs when male and female gametes meet: • copulation, coitus, sexual intercourse • Restores the diploid number (2n)

7. Comparison of the Female and Male Reproductive Systems • Primarily nonfunctional and “dormant” until puberty. • At puberty, external sex characteristics become more prominent. • breast enlargement in females • fat distribution patterns in both sexes • pubic hair in both sexes • reproductive organs become fully functional • gametes mature • gonads secrete sex hormones • Both reproductive systems produce gametes.

8. Comparison of the Female and Male Reproductive Systems • Puberty: • Initiated by hypothalamus • Secretes GnRH (gonadotropin-releasing hormone • Stimulates release of FSH and LH • Prior to puberty, not present • Stimulate gonads to produce: • Sex hormones • gametes

9. Comparison of the Female and Male Reproductive Systems • Female typically produces and releases a single oocyte monthly. • Maleproduces 100,000,000’s of (sperm) daily. • male gametes are stored for a short time • if they are not expelled from the body within that period, they are resorbed

11. Perineum • Diamond-shaped area between the thighs that is circumscribedanteriorly by the pubic symphysis, laterally by the ischial tuberosities, and posteriorly by the coccyx. • 2 distinct triangle bases • formed by an imaginary horizontal line extending between the ischial tuberosities of the ossa coxae. • Anterior triangle, or urogenital triangle • contains the urethral and vaginal orifices in females • contains the base of the penis and the scrotum in males. • Posterior triangle, or anal triangle • location of the anus in both sexes.

13. Anatomy of the Female Reproductive System • Peritoneum folds around the various pelvic organs and creates two major dead-end recesses, or pouches. • anterior vesicouterine pouch forms the space between the uterus and the urinary bladder • posterior rectouterine pouch forms the space between the uterus anteriorly and the rectum posteriorly • Primary sex organs of the female are the ovaries. • Accessory sex organs include • uterine tubes • uterus, • vagina, • clitoris • mammary glands.

15. Mesovarium: • Double folds of peritoneum • Attaches ovaries to broad ligament • Broad ligament • Peritonium • Drapes over the uterus • Ovarian ligament • Ovary to uterus • Suspensory ligament • Ovary to pelvic wall

18. Ovarian Follicles • Within the cortex are thousands of ovarian follicles. • Consist of • Follicle cells • granulosa cells • nurse cells that support the oocyte • a type of oocyte. • Several different kinds of ovarian follicles, each representing a different stage of development. • Oogenesis: • maturation of a primary oocyte to a secondary oocyte.

21. Before Birth • The process of oogenesis occurs in a female fetus before birth. At this time, the ovary contains primordial germ cells called oogonia, which are diploid cells, meaning they have 23 pairs of chromosomes. • During the fetal period, the oogonia start the process of meiosis, but they are stopped at prophase I. At this point, the cells are called primary oocytes. • At birth, the ovary of a female child is estimated to contain approximately 1.5 to 2 million primordial follicles within its cortex. • The primary oocytes in the primordial follicles remain arrested in prophase I until after puberty.

22. From Puberty to Menopause • During childhood ovaries are inactive, and no follicles develop. • Atresia occurs, in which some primordial follicles regress or break down. • By the time she reaches puberty only about 400,000 primordial follicles remain. • At puberty, the hypothalamus releases GnRH (gonadotropin-releasing hormone), which stimulates the anterior pituitary to release FSH (follicle-stimulating hormone) and LH (luteinizing hormone). • The levels of FSH and LH vary in a cyclical pattern and produce a monthly ovarian cycle. • The three phases of the ovarian cycle: are the follicular phase, ovulation, and the luteal phase.

23. The Three Phases of the Ovarian Cycle • Follicular phase occupies days 1–13 of an approximate 28-day ovarian cycle. • Ovulation occurs on day 14 of a 28-day ovarian cycle and is defined as the release of the secondary oocyte from a vesicular follicle. • only one ovary ovulates each month • Luteal phase occurs during days 15–28 when the remaining follicle cells in the ruptured vesicular follicle turn into a corpus luteum. • secretes progesterone and estrogen that stabilize and build up the uterine lining, and prepare for possible implantation of a fertilized oocyte • has a life span of about 10–13 days if the secondary oocyte is not fertilized • it regresses and becomes a corpus albicans • the uterine lining to be shed as menstruation • menarche

25. After Menopause • The time when a woman is nearing menopause is called perimenopause. • estrogen levels begin to drop, and • a woman may experience irregular periods, skip some periods, or have very light periods • When a woman has stopped having monthly menstrual cycles for 1 year and is not pregnant, she is said to be in menopause. • The age at onset typically is between 45 and 55 years • follicles stop maturing, and significant amounts of estrogen and progesterone are no longer being secreted • a woman’s endometrial lining does not grow, and she no longer has a menstrual period

29. Uterine Tubes • The uterine tubes, also called the fallopian tubes or oviducts, extend laterally from both sides of the uterus toward the ovaries. • In these tubes, the secondary oocyte is fertilized, and the pre-embryo begins to develop as it travels toward the uterus. • Usually it takes the pre-embryo about 5 to 6 days to reach the lumen of the uterus. • Parts: lined with mucosa (simple ciliated columnar ep), muscularis, serosa • Infundibulum • Ampulla • Isthmus • Interstitial segment

30. The Uterus Serves Four Functions • Site for implantation. • pre-embryo implants into the inner uterine wall and becomes connected to the uterine lining • Supports, protects, and nourishes the developing embryo/fetus • forms a vascular connection with the mother’s uterine wall that later develops into the placenta • Ejects the fetus at birth after maternal oxytocin levels increase to initiate the uterine contractions of labor. • Site for menstruation. • if an oocyte is not fertilized or after a baby is expelled, the muscular wall of the uterus contracts and sheds its inner lining as menstruation

31. Regions of the Uterus • Fundus • Body • Isthmus • Cervix • Cervical canal • Internal os • External os

32. Support of the Uterus • Pelvic floor muscles • Pelvic diaphragm • Urogenital diaphragm • Round ligaments • Lateral uterus, through inguinal canal, to labia majora • Maintain anteverted position • Transverse cervical ligaments • Lateral cervix and vagina to pelvic wall • Uterosacral ligaments • Inferior uterus to sacrum

33. Wall of the Uterus • Composed of three concentric tunics: • Perimetrium • Myometrium • Endometrium • The outer tunic of most of the uterus is a serosa called the perimetrium. • continuous with the broad ligament • The myometrium is the thick, middle tunic of the uterine wall formed from three intertwining layers of smooth muscle. • in the nonpregnant uterus, the muscle cells are less than 0.25 millimeters in length • during the course of a pregnancy, smooth muscle cells increase both in size and in number

34. Uterine (Menstrual) Cycle and Menstruation • The menstrual phase occurs approximately during days 1–5 of the cycle. This phase is marked by sloughing of the functional layer and lasts through the period of menstrual bleeding. • The proliferative phase follows, spanning approximately days 6–14. The initial development of the functional layer of the endometrium overlaps the time of follicle growth and estrogen secretion. • The last phase is the secretory phase, which occurs at approximately days 15–28. During the secretary phase, increased progesterone secretion from the corpus luteum results in increased vascularization and development of uterine glands. • If the oocyte is not fertilized, the corpus luteum degenerates, and the progesterone level drops dramatically. • Without progesterone, the functional layer lining sloughs off, and the next menstrual phase begins.

35. Vagina • The vagina is • thick-walled, fibromuscular tube • forms the inferior-most region of the female reproductive tract • measures about 10 centimeters in length in an adult female. • The vagina connects the uterus with the outside of the body anteroventrally • functions as the birth canal. • Also the copulatory organ of the female • Serves as the passageway for menstruation. • The vaginal wall is heavily invested with both blood vessels and lymphatic vessels. • The vagina’s relatively thin, distensible wall consists of three tunics: • an inner mucosa, a middle muscularis, and an outer adventitia

36. External Genitalia • The external sex organs of the female, are collectively called the vulva. • The mons pubis is an expanse of skin and subcutaneous connective tissue immediately anterior to the pubic symphysis. • covered with pubic hair in postpubescent females • labia majora • labia minora • Contain the vestibule • Urethral orifice • Vaginal oriface • Clitoris located at the anterior regions of the labia minora • glans • prepuce−an external fold of the labia minora that forms a hoodlike covering over the clitoris.

38. Mammary Glands • Each mammary gland, or breast, is located within the anterior thoracic wall and is composed of a compound tubuloalveolar exocrine gland. • Breast milk contains proteins, fats, and a sugar to provide nutrition to infants. • The nipple is a cylindrical projection on the center of the breast. It contains multiple tiny openings of the excretory ducts that produce breast milk. • The areola is the pigmented rosy or brownish ring of skin around the nipple. Its surface often appears uneven and grainy due to the numerous sebaceous glands immediately internal to the surface. • The color of the areola may vary, depending upon whether or not a woman has given birth. In a nulliparous woman (a woman who has never given birth), the areola is rosy or light brown in color. • In a parous woman (a woman who has given birth), the areola may change to a darker rose or brown color.

41. Anatomy of the Male Reproductive System • Primary organs: gonads are the testes • Accessory sex organs include: • a complex set of ducts and tubules leading from the testes to the penis • a group of male accessory glands • the penis, which is the organ of copulation

43. Scrotum • Skin covered sac • Raphe: external midline seam • Continues on inferior surface of the penis, and to anus. • Components of scrotal wall. • Skin • Fascia • Dartos muscle • External spermatic fascia • Cremaster muscle • Internal spermatic fascia • Tunica vaginalis.

44. Scrotum • Male gametes are sensitive to elevated temperatures • often exhibit abnormal or completely curtailed development • Gamete development occurs outside the body • Scrotum: a skin-covered sac that houses: • male gonads • first portion of the duct system • site of early sperm maturation and development, reside outside the body proper. • Testes exposed to elevated temperatures • Skin of the scrotal sac becomes thin • result of dartos muscle relaxation. • The cremaster muscle relaxes • allows the testes to move inferiorly away from the body • The testes temperature becomes less than normal body temperature. • The opposite occurs if the testes are exposed to cold.

47. Testes • Small, oval organ • Housed in the scrotum • Produces: • Sperm • androgens. • Coverings • Serous membrane called tunica vaginalis • Parietal layer • Visceral layer. • Tunica albuginea • Forms internal septa • 250 lobules per testis • Each lobule has up to 4 seminiferous tubules • Two types of cell • Sustentacular cells • Germ cells • Interior is called mediastinum testis.

49. Testes • Blood-testis barrier • Tight junctions between sustentacular cells • Spern develop in the semineferous tubules • Interstitial spaces: surround the seminiferous tubules. • Contain interstitial (Leydig) cells • produce hormones called androgens. • Several types of androgens • most common one is testosterone. • the adrenal cortex secretes a small amount of androgens • the vast majority of androgen release is via interstitial cells in the testis • beginning at puberty. • These hormones cause males to develop the classic characteristics: • axillary and pubic hair • deeper voice • sperm production.