Reproductive System: Functions of Male and Female Organs

1. Reproductive System YaoYang, Physiology department of SMC www.themegallery.com

2. The term “reproduction” usually means formation of new living entities, which closely resemble to the parent species. In higher animals, reproduction is accomplished by activities of both sexual organs of male and female. The processes are very complex including production of sperms and ova, sexual intercourse, fertilization of ovum, pregnancy, development of fetus and lactation.

3. Section 1 Reproductive and Hormonal Functions of the Male

4. Testes • Produce 2-4 million sperm every day • Outside body – why? • Sperm like temps 1-2 cooler than body temp Functions of testes: spermatogenesis in seminiferous tubules secrete hormones: leydig cell-testosterone Sertoli cell-inhibin.

5. I. Endocrine Function of Testes • Androgens • Testes secrete several male sex hormones, which are collectively called androgens, including testosterone, dihydrotesterone and androstenedione. • Testosterone is so much more abundant than the others that one can consider it the significant testicular hormone.

6. (1) Functions of testosterone 1) Maintenance of spermatogenesis 2) Stimulation of development of genitalia. 3) Development and maintenance of the male secondary sexual characteristics. 4) Maintenance of libido. 5) Effect on metabolism. increases anabolism of protein, causes growth of the bones in the thickness, deposition of calcium salts enhancement of production of red cells.

7. 2. Inhibin Inhibin, a glycoprotein with a molecular weight of 31,000-32,000, has a potent inhibitory effect on FSH secretion by pituitary gland. The effect of inhibin on hypothalamus is slightly inhibitory in GnRH secretion.

8. II. Regulation of Testis Function • Hypothalamic-Pituitary-Testis Axis • GnRH • stimulate the synthesis and release the two gonadotropins, LH and FSH. Hypothalamus GnRH Anterior pituatory FSH L H testis seminiferous tubules Sertoil Leydig (2) LH (Luteinizing hormone) LH causes interstitial cell of Leydig to synthesize testosterone by activating the cAMP second message system and to release testosterone. T sperm inhibin ABP E2

9. (3) FSH (follicle stimulating hormone) FSH stimulates Sertoli cells to produce ABP (androgen binding protein). ABP binds with testosterone and enters the seminiferous tubule, increasing the androgen concentration in tubule and promoting spermatogenesis. FSH stimulates Sertoil cell to produce and secrete inhibin, which plays a negative feedback mechanism for control of testis function.

10. 2 Inhibin Inhibin has a strong direct effect on the anterior pituitary gland in inhibiting FSH secretion and a slight effect on the hypothalamus in inhibiting GnRH secretion. These automatic feedback mechanisms can maintain a normal speed of spermatiogenesis, which is required for male reproduction function.

11. Section 2 Reproductive and Hormonal Functions of the Female

12. Organs and Function • Ovaries –2 female sex glands Produce egg cells Produces the hormone, estrogen • Uterus Muscular pear-shaped organ Where baby develops • Fallopian Tubes Egg travels through these 2 tubes to the uterus • Cervix Opening between the uterus & vagina • Vagina Muscular tunnel from cervix to outside

13. Menstruation, Ovulation and Hormonal Regulation • The normal reproductive years of the female are characterized by monthly rhythmical changes of secretion of the female hormones and corresponding changes in the ovaries and sexual organs. • This rhythmical pattern is called the female sexual cycle of menstrual cycle, which may be regarded as periodic preparation for fertilization and pregnancy. • Its most conspicuous feature is the periodic vaginal bleeding that occurs with the shedding of the uterine mucosa, which is known as menstruation. • .

14. Uterine Cycle • Proliferative phase (estrogen phase) • Secretary phase (progesterone phase) • Menstruation

15. Ovarian Cycle • Follicular phase • Ovulation • Luteal phase

17. II. Endocrine Functions of Ovaries • Functions of Estrogen • On sexual organs. • The principle function of estrogen is to cause cellular proliferation and growth of the tissues of the sex organs and other tissues related to production. • Estrogen stimulates the developmentof sexual organs including ovaries, fallopian tubes, uterus, vagina and the external genitalia.

18. (2) On secondary female sexual characteristics. Estrogen stimulates development of the secondary sex characteristics of female such as feminine figure, soft and smooth skin. It cause the breast to grow and to show mature appearance. (3) On metabolism. Estrogen causes a slight increase in total body protein, which result in growth-promoting effect on the sexual organs, the bones, the breasts and a few other tissues. Estrogen has a slight effect on retention of water and sodium by the kidney tubules.

19. 2. Progesterone • Effect on uterus. • Progesterone promote secretary changes in the uterine endometrium, thus preparing the uterus for implantation of the fertilized ovum and providing nutrition for the early dividing ovum. • Progesterone decreases excitability and sensitivity to oxytocin of myometrium. • It decreases the frequency and intensity of uterine contractions, thereby helping to prevent expulsion of the implanted ovum.

20. (2) Effect on breasts. Progesterone promotes development of the tubules and alveoli of the breasts, causing the alveolar cells to proliferate, enlarge, and become secretary nature but not to secrete milk. (3) Thermogenic effect. Progesterone causes thermogenic effect and is responsible for the rise in basal body temperature at the time of ovulation. (4) Progesterone relaxes the smooth muscle of the blood vessels and digestive tracts.

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