Reproduction

1. Reproduction Male Reproductive System Female Reproductive System Implantation and Pregnancy

3. 11.1 Male Reproductive System

4. Inside the Scrotum Male external genitalia consist of two structures; the scrotum containing the testes, and the penis These are the beginning and the end of the route that sperm cells take through the male system Sperm are produced in the seminiferous tubules of the testes by a process called spermatogenesis

5. Within the lining of these tubes is a specialized layer of cells called the ‘germ layer’ Sperm cells are derived from these unspecialized cells, which continuously divide by mitosis One daughter cell remains as the new germ cell; the other daughter cell moves towards the inner wall of the tubule and divides by meiosis to form cells, which eventually become sperm

6. Spermatogenesis begins in the seminiferous tubules but the developing sperm move through the lumen of the tubules to the epididymis Video

7. Each testis has an epididymis on one side of its surface that contains a coiled tube formed by seminiferous tubules after they join together The tubes of the epididymis lead into the ductus (vas) deferens The epididymis and the ascending portion of the vas deferens are the final maturation sites for sperm

8. Sperm It is in these regions of the tubules that sperm gain their swimming ability, the whole process takes a few days After puberty, spermatogenesis is ongoing, millions of sperm cells develop every day throughout a male’s reproductive life

9. Mature sperm have three identifiable regions: • The head • The mid-piece • The tail

10. The head contains the DNA (23 chromosomes) It is encapsulated by the acrosome, a gel-like covering, which not only provides sperm with a chemical guidance system while swimming but also with enzyme capabilities required for penetrating an ovum (egg)

11. The mid-piece of a sperm contains mitochondria, which produce ATP required for the swimming activity The tail (a flagellum) provides the locomotion

12. Testosterone Functions Each testis also contains endocrine tissue located between the seminiferous tubules called interstitialcells that secrete androgens (male sex hormones), including testosterone Testosterone is essential for the maturation of the primary sex organs and development of the secondary sex characteristics associated with puberty

13. The secondary sex characteristics in males include ancillary hair growth, enlargement of the larynx, muscle and skeletal growth, release of oils and sweat (potentially causing acne and BO), and baldness (given appropriate genetics) A portion of the adrenal cortex also produces androgens; in this way, the adrenal cortex contributes to muscle mass and strength in both males and females

14. Penis The penis is the organ of copulation; it contains erectile tissue and the urethra (this portion of the urethra serves a dual purpose) It not only conducts urine to the outside for excretion, but also carries sperm during ejaculation

15. During sexual arousal, the arteries of the penis dilate (due to parasympathetic stimulation), and the veins constrict engorging the erectile tissue with blood making the penis erect The changed angle of the penis allows sperm, bathed in seminalfluid, to enter the urethra

16. Seminal Fluid The seminal fluid is a milky white solution contributed to by three glands: seminalvesicles, Cowper’s gland, and the prostategland It has a pH of 7.5, contains fructose to nourish the sperm, HCO3- as a buffer, and a lipid-based chemical messenger called prostaglandins (promotes uterine contractions)

17. When semen (sperm plus seminal fluid) enters the urethra it promotes the rhythmic contractions leading to ejaculation A sphincter at the base of the bladder is closed during this time, so that urine cannot enter the urethra After ejaculation, the penis returns to its normal flaccid state for the duration of a refractoryperiod

18. Hormones With puberty the hypothalmus begins to promote the sexual functions of the testes through the release of gonadotropic releasing hormones (GnRHs) to the anterior pituitary The anterior pituitary responds by releasing two hormones: luteinizing hormone (LH) and follicle stimulating hormone (FSH)

19. LH promotes the production of testosterone from the interstitial cells, where FSH promotes the maturation of sperm Testosterone is maintained at a fairly constant level by negative feedback while high levels of testosterone inhibit the hypothalamus and the pituitary from releasing their hormones

20. 11.2 Female Reproductive System

21. The ovaries are the structures where ova (ovum) are produced The female reproductive tract consists of the oviducts, uterus, and vagina This tract does not meet up with the urethra as it does in males

22. Oogenesis Oogenesis is the development of ova; at birth, a female has several hundred thousand immature ova in structures called follicles in the cortical regions of her ovaries After puberty these mature (roughly one a month) over her reproductive life Only a few hundred ever mature

23. As a follicle matures, it undergoes changes to house the ovum in a fluid filled space This development increases until the structure bulges out from the ovary surface At this point the follicle is mature and is known as a Graafianfollicle

24. Ovulation, the bursting of the follicle and the release of the ovum, is under hormonal control The ovum is directed into the oviduct by the undulations of the fimbriae at the opening of the oviduct The oviduct is a muscular tube that is lined with cilia that sweeps the fluid towards the uterus

25. In this manner the ovum (which has no means of locomotion itself) is moved over a period of four or five days, along the female tract The remaining follicular structure in the ovary develops into a glandular tissue known as the corpus luteum

27. Womb The uterus is sometimes called the womb (a thick-walled muscular pear-shaped organ) The inner lining (endometrium) has two layers: a basal layer, which is adjacent to the muscle and elastic fibers, and a functional inner lining The thickness of the inner lining varies according to a hormonally controlled reproductive cycle Video

28. Review Which of these is a male primary sex characteristic? Deepening of the voice Facial and pubic hair growth External reproductive organs Muscle and skeletal development

29. Which of these is a male primary sex characteristic? Deepening of the voice Facial and pubic hair growth External reproductive organs Muscle and skeletal development

30. After sperm cells are produced, they are stored mainly in the Urethra Prostate Epididymis seminal vesicles

31. After sperm cells are produced, they are stored mainly in the Urethra Prostate Epididymis seminal vesicles

32. Reducing of the release of GnRH from the hypothalamus will stimulate LH and FSH secretion. decrease the release of gonatotropic hormones stimulate an increase in progesterone and estrogen levels initiate ovulation in females and reduce spermatogenesis in males.

33. Reducing of the release of GnRF from the hypothalamus will stimulate LH and FSH secretion. decrease the release of gonatotropic hormones stimulate an increase in progesterone and estrogen levels initiate ovulation in females and reduce spermatogenesis in males.

34. Which of the following produces testosterone? Sperm cells Hypothalamus Interstitial cells Anterior pituitary

35. Which of the following produces testosterone? Sperm cells Hypothalamus Interstitial cells Anterior pituitary

36. Which of the following BEST describes how an ovum enters an oviduct once ovulation occurs? It swims Peristalsis It is drawn in the action of fimbriae and cilia It is propelled by the force of the bursting follicle

37. Which of the following BEST describes how an ovum enters an oviduct once ovulation occurs? It swims Peristalsis It is drawn in the action of fimbriae and cilia It is propelled by the force of the bursting follicle

38. Vagina The vagina is the tube that extends from the cervix (neck of the uterus) to the outside Its inner lining consists of mucosal cellsand serves as the birth canal as well as the female organ of copulation

39. The clitoris is the female structure that is homologous to the penis in males (located at the anterior end of the labia, folds of skin, that surround the vaginal opening) Where the male penis becomes engorged with blood during sexual arousal, the clitoris, labia and vaginal walls of the female become engorged

40. Hormones FSH stimulates the maturation of an ovum in the ovary LH stimulates the secretion of progesterone and estrogen from other cells of the follicle Progesterone stimulates the maturation of the endometrium lining of the uterus

41. Estrogen It is necessary for egg maturation and also for the development of secondary sex characteristics:uterine cycle, fat and hair distribution, growth of the uterus and vagina, pelvic growth, and it contributes to breast development, along with progesterone As secretion of estrogen increases, the levels of LH and FSH begin to decrease until the follicle is mature in which there is a sharp increase in LH and (to a lesser extent) FSH

43. Ovulation It is believed that this significantly high level of estrogen exerts positive feedback on the hypothalmus, thus causing a surge of LH (and FSH) resulting in ovulation After ovulation, the corpus luteum temporarily retains an endocrine function secreting estrogen which stimulates the continues thickening of the endometrium

44. Progesterone stimulates the endometrium to become secretory The changes to the endometrium are to prepare for the possibility of fertilization and pregnancy If fertilization does not occur, the corpus luteum degenerates after about ten days

45. Menstruation When it degenerates, the levels of estrogen and progesterone drop suddenly and the endometrium that was built up and maintained is shed The shedding of the endometrium (mostly blood tissue) is known as menstruation (menses) The period of menses typically lasts about five days

46. During menses, the anterior pituitary begins to release LH and FSH and the cycles of change that occur in the ovaries and uterus begin again

48. Ovarian and Uterine Cycles

49. 11.3 Implementation and Pregnancy

50. Fertilization During copulation semen (containing as many as 400 million sperm) is ejaculated into the vagina and begin to swim towards the ovaries An ovum is only viable for fertilization for six to twenty-four hours after ovulation, hence fertilization usually occurs in the oviduct