Human Reproduction

1. Human Reproduction • Male Reproductive Anatomy • Spermatogenesis and Male Hormones • Male Reproductive Technologies and Birth Control • Female Reproductive Anatomy • Oogenesis and Female Hormones • Uterine and Ovarian Cycles • Development of the Fetus • Parturition and Lactation • Teratogens and Birth Defects • Reproductive Technologies

2. Reproduction • ensures the survival of a species • Sexual reproduction produces offspring with new and unique characteristics that may increase their chance of survival.

3. Reproduction • 2 types of gametes (sex cells) • Males: 1 billion sperm each day from the ages 13-90 • Females: born with 400, 000 eggs, 400 mature from ages 12 to 50

4. Reproduction • The average gestational period for a human is 266 days.

5. Male Reproductive System • The male reproductive structures are responsible for: • producing sperm • storing sperm • delivering sperm to the female

6. Male Reproductive System

7. Male Reproductive System • Scrotum • holds the testes away from the body to keep them cool. • Sperm production only occurs at temperatures about 3 degrees below body temperature.

8. Male Reproductive System Testis • descend about 2 months before birth • spermatogenesis • seminiferous tubules produce sperm • Interstitial cells secrete testosterone

9. Male Reproductive System • Epididymis – holds sperm for about 2-4 days while they mature

10. Male Reproductive System Vas Deferens • conducts sperm during ejaculation • vasectomy: the vas deferens cut and tied off, to prevent conduction of sperm.

11. Male Reproductive System • Ejaculatory Duct –propels semen and sperm through the urethra. • Urethra –conduction of urine and semen out of the penis. • a sphincter muscle closes off the bladder, preventing urine from exiting the urethra.

12. Male Reproductive System Penis • male organ for copulation. Beneath the skin, lies the urethra surrounded by spongy protective tissue that expands to form the glans penis. • Prepuce (foreskin) – is a loose sheath of skin covering the glans penis of uncircumcised males. The foreskin produces an oily secretion known as smegma.

13. Seminal Fluid Is produced by three different glands: • Seminal Vesicles • fluid high in fructose that provides energy sperm need to swim • Prostaglandins which cause contractions of muscles in the female reproductive tract to help move sperm in

14. Seminal Fluid • Prostate Gland • milky white alkaline fluid that neutralizes the acidity of the vagina • Cowper’s Gland • buffered fluid that cleanses and neutralizes the acidity in the urethra

15. Spermatogenesis • Spermatozoa – are the smallest cells in the body. They have very little cytoplasm in the head, and a large tail (flagellum).

16. Spermatogenesis • Spermatogonia – undifferentiated germ cells that have 46 chromosomes • Primary Spermatocytes – larger cells that undergo meiosis I

17. Secondary spermatocytes – cells that undergo meiosis II Spermatids – cells with 23 chromosomes, that are ready to mature in the epididymis Spermatozoa – mature sperm cells

18. Sertoli Cells- nourish sperm cells

20. Terminology Erection • parasympathetic nerve impulses dilate the arteries of the penis, allowing blood to flow rapidly into the highly vascular penile tissue • veins are compressed preventing blood from leaving the penis. • Erection

21. Terminology • Ejaculation – occurs when sexual stimulation forces semen to the urethra, where rhythmical muscle contractions cause the semen to be expelled from the penis. • Infertility – the inability to produce viable sperm. • Impotency – the inability to achieve a sustained erection.

22. Regulation of the Male Reproductive Hormones

23. Male Reproductive Hormones • GnRH : gonadotropic releasing hormone • released from hypothalamus • stimulates the anterior pituitary to release LH and FSH • LH : luteinizing hormone • stimulates the interstitial cells (cells in between seminiferous tubules) of the testes to produce testosterone

24. Male Reproductive Hormones • Testosterone – responsible for male secondary sex characteristics, required for sperm production (larger larynx, growth of penis, body hair, muscles…) • FSH: follicle stimulating hormone • stimulates production of sperm in the seminiferous tubules

25. Male Reproductive Hormones • Inhibin • produced by Sertoli cells when sperm count is high • Sends feedback to inhibit FSH and GnRH

27. Female Reproductive Structures • The female reproductive structures are responsible for • reception of sperm • producing an egg • nourishing and protecting the fetus • delivering the baby

28. Female Reproductive Structures

29. Female External Structures (Vulva) • Labia majora – large, fatty, hair covered folds that protect the genitals • Labia minora – smaller folds of skin inside the labia that are kept moist by secretions • Clitoris – small shaft of erectile tissue

30. Female Internal Structures • Vagina • intercourse : accepts the penis • birth canal during labor • pH is generally acidic

31. Female Internal Structures • Cervix • Thick muscular tissue • plugs closed with mucous during pregnancy • prevents material from getting into the uterus, and holds the baby in

32. Female Internal Structures • Uterus (womb) • pear shaped muscular organ (5 cm wide) • houses the developing fetus during pregnancy (30 cm wide) • strong contractions help push the baby out during birth

33. Female Internal Structures • Ovaries • produce the ovum from follicles found in the outer cortex

34. Female Internal Structures • Oviducts /Fallopian tubes • conduction of the ovum (egg) from the ovaries to the uterus • where fertilization usually takes place • If egg implants here = ectopic pregnancy frequency

35. Female Internal Structures • Fimbriae • small fingerlike projections at the ends of the oviducts that sweep to draw the egg into the fallopian tube

36. Female Internal Structures

37. Ovarian Structures • Follicle • cells that support and protect the ovum • secrete estrogen to mature the ovum • become a corpus luteum following ovulation. • Ovum – egg cell, viable for about 24 hours after release.

38. Ovarian Structures • Corpus Luteum • cells remaining after a follicle has ruptured during ovulation • secretes progesterone and some estrogen for about 3 months if fertilization and pregnancy occurs • deteriorates after about 8 days if fertilization does not occur.

39. Oogenesis

40. Regulation of the Female Reproductive Hormones • GnRH – stimulates the anterior pituitary to produce FSH and LH • FSH – stimulates development of the follicle and the production of estrogen within the ovary

41. Regulation of the Female Reproductive Hormones • LH – causes ovulation, development of the corpus luteum which secretes progesterone

42. Reproductive Hormones • Estrogen • secreted by the follicles in the ovaries • causes maturation of the egg • stimulates growth of the endometrium (uterus lining) • Female secondary sex characteristics • Inhibits FSH

43. Reproductive Hormones • Progesterone • secreted by the corpus luteum • continues preparation of endometrium • inhibits both FSH and LH to preventovulation • prevents uterine contractions • firms the cervix

44. P 525 Fig 6

45. The Uterine and Ovarian Cycles

46. Day 1-5: Menstruation/Flow Phase • Estrogen and progesterone levels are low • endometrium is sloughed off and shed Day 1-13:Follicular Phase • FSH secreted from ant. pit. promotes development of the follicle • follicle releases estrogen, which promotes growth of the endometrium.

47. Day 14: Ovulation • An increase in LH causes the ovum to be released • FSH is lowered Day 15 – 28: Luteal Phase • LH promotes formation of the corpus luteum • corpus luteum produces progesterone, inhibits GnRH, LH and FSH, preventing subsequent ovulation.

48. Many birth control pills are high in progesterone which prevents ovulation • cancer

50. No Fertilization  corpus luteum degenerates, estrogen and progesterone levels drop, and menstruation occurs.