Reproductive System

1. Reproductive System Chapter 22 Continued

2. Female Reproductive System • Ovaries – gonads – produce oocytes and hormones • Uterine (Fallopian) tubes or oviducts • Uterus • Vagina • Vulva (female external reproductive organs)

4. Ovaries • Located in upper pelvic cavity, on either side of uterus • Held in place by a number of ligaments • Descend from abdominal cavity to pelvic brim

7. Each ovary has a hilus – blood vessels and nerves enter • Several layers: • Germinal epithelium – simple squamous cells • Tunica albuginea- white capsule of C. T. • Stroma – connective tissue, can be divided into: • Medulla – loose connective tissue, blood vessels, nerves • Cortex - contains ovarian follicles – consist of oocytes at various stages of development

8. Single layer – follicular cells • Several layers – granulosa cells • Mature or Graafian follicle is a large, fluid-filled follicle that will rupture and release a secondary oocyte in process called ovulation. • Corpus luteum is the remnant of a ruptured follicle – produces estrogen, progesterone and relaxin until degenerates into the corpus albicans.

10. Oogenesis • During fetal development, germ cells differentiate into oogonia  millions of germ cells. • Many degenerate, but a few develop into primary oocytes that enter Prophase I of meiosis before birth – stop there. • At birth, about 1 million oogonia and primary oocytes in each ovary • About 400 mature over a woman’s lifetime.

11. Primordial follicle – primary oocyte and single layer of follicular cells • Under influence of FSH, become primary follicles which have several layers of cells. • Layer of glycoprotein, the zona pellucida, separates oocyte from the granulosa cells. • Ovarian cells outside follicle form two layers: • Inner vascular layer (theca interna) that secretes hormones • Outer fibrous layer (theca externa) – connective tissue.

13. Granulosa cells begin to secrete fluid, forms a cavity called the antrum. • Now called a secondary follicle. • After puberty, each month one secondary follicle resumes meiosis. • Meiosis I results in two unequal cells – secondary oocyte and a polar body. • Begins to divide again but stops at metaphase II.

16. At ovulation, secondary oocyte and polar body are released. • If not fertilized, degenerates. • If penetrated by sperm, meiosis resumes, forming ovum and another polar body. • Nuclei of ovum and sperm unite to form a zygote. (2n or diploid) • So, meiosis results in ONE OVUM and three polar bodies (which degenerate)

23. Uterine (Fallopian) Tubes • Extend laterally from uterus • Open end is funnel shaped – infundibulum • Many finger-like projections – fimbriae • Local currents producedby movement of fimbriae draws ovum into uterine tube. • Uterine tube is lined with ciliated columnar epithelium, which move ovum along. • Peristaltic movements also propel ovum toward uterus.

25. The secondary oocyte is usually fertilized in the outer one-third of the uterine tube, although fertilization may occur in the abdominopelvic cavity. • Fertilization can occur up to about 24 hours after ovulation. • If oocyte is fertilized, it will reach the uterus in about 7 days.

27. The Uterus • Is an organ about the size and shape of an inverted pear. • Functions in menstruation, implantation of zygote, development of the fetus, and labor. • Also part of the pathway for sperm to reach ovum. • Normally held in position by ligaments

29. Uterus can be divided into the fundus, body and cervix. • Secretory cells of the cervix produce about 20 – 60 ml of mucus / day. • At time of ovulation, this mucus becomes thinner and more alkaline. • Mucus provides for the energy needs of the sperm, protects sperm from environment of the vagina, and protects them from phagocytes. • At other times, mucus becomes thick and can form a cervical plug which impedes passage.

30. Layers of uterus : perimetrium, myometrium and endometrium • Perimetrium – a part of visceral peritoneum • Myometrium – bulk of uterus – three layers of muscle that contract under influence of oxytocin during labor. • Endometrium – highly vascular mucosa • Stratum functionalis – shed during menstruation • Stratum basalis – deeper, permanent layer, gives rise to new stratum functionalis after each cycle.

32. The Vagina • Passageway for sperm and menstrual flow • Receptacle for penis during intercourse • Inferior portion of birth canal • Capable of considerable distention (stretching) • Mucosa is continuous with that of uterus and consists of nonkeratinized stratified squamous epithelium. • Contains large stores of glycogen which decomposes to organic acids – lower pH = less susceptible to infection & less hospitable to sperm

34. The Vulva • External genitals of female • Mons pubis – pad of adipose tissue which cushions pubic symphysis • Labia majora (labium majus) – folds of skin analogous to the scrotum • Adipose tissue, sebaceous glands, sweat glands • Labia minora (labium minus) – folds of skin with many blood vessels and sebaceous (oil) glands

35. Clitoris – homologous to the penis, also composed of two corpora cavernosa and a glans. • Vestibule – between the labia minora • External urethral orifice • Openings for ducts of paraurethral glands : secrete mucus and are homologous to prostate • Beside vaginal orifice are the vestibular (Bartholin’s) glands – produce mucus during arousal – homologous to bulbourethral glands

38. Female Reproductive Cycle • Two cycles: • Ovarian cycle – leading to maturation and release of oocyte • Uterine or menstrual cycle – prepares uterus to receive the fertilized ovum. • Both controlled by GnRH from the hypothalamus, which stimulates release of FSH and LH. • Estrogen and progesterone are produced by the ovaries.

39. Estrogens • Stimulate the growth, development, and maintenance of female reproductive structures, secondary sex characteristics and the breast. • They help regulate fluid and electrolyte balance. • The stimulate protein synthesis • They lower blood cholesterol levels

40. Moderate levels of estrogen in the blood inhibit the release of GnRH, LH and FSH. • This is the basis for the birth control pill.

41. Progesterone • Is secreted mainly by the corpus luteum and works with estrogen to prepare the endometrium for implantation and mammary glands for lactation. • High levels of progesterone also inhibit GnRH, LH and FSH.

42. Relaxin • Produced by the corpus luteum • Inhibits uterine contractions which aids implantation. • During pregnancy, it is produced by the placenta, and continues to relax uterine smooth muscle. • Also relaxes the pubic symphysis and helps dilate the uterine cervix for delivery.

43. Phases of the Female Reproductive Cycle • Type cycle runs 24 -35 days, 28 days ave. • Three phases: • Menstrual phase • Preovulatory phase • Postovulatory phase

44. Menstrual phase • Days 1 – 5 • FSH release stimulates the maturation of follicles. 20 or so follicles, some in each ovary begin to enlarge. • In the uterus, the stratum functionalis is shed, discharging 50 -150 ml of blood, tissue fluid, mucus and epithelial cells. • Declines of estrogen and progesterone cause the spiral arteries to constrict, cells become ischemic and die, and are sloughed off.

46. Preovulatory phase • Most variable in length, us. Day 6 – 13 • Follicles continue to grow, granulosa cells produce increasing amounts of estrogen and some progesterone. This causes LH to be secreted, but stored in the pituitary. • Dominant follicle secretes inhibin, inhibiting growth of other follicles, and continues to develop into a mature follicle. • Called follicular phase in ovary.

47. In the uterus, the estrogens produced by the developing follicles cause the cells of the stratum basalis to produce a new stratum functionalis, and thickness of endometrium doubles. • Proliferative phase in uterus.

49. Ovulation • About day 14, when estrogen levels are high enough, cause anterior pituitary to release a surge of LH that lasts about 36 hours. • This is what ovulation tests measure. • LH weakens wall of follicle, and ovulation occurs. • Secondary oocyte is released into pelvic cavity, taking the zona pellucida and first layer of granulosa cells.