Understanding the Reproductive System for Healthy Living

1. Bio11 schedule Lecture: Reproductive system Lecture exam 2 - Thursday Feb 24 Same format as before Covers Ch 5-8, 11-15 Study guide is posted Posted: Your total points so far (your “grade” in class) Last day to drop with a “W” is this Fri 2/25 Extra credit is due Thur Mar 3

2. Ch 16 Reproductive System Males & Females Embryonic Development Family planning HIV/AIDS

3. The male reproductive system • Designed for the continuous production of a large number of sperm • Produces testosterone, the male sex hormone

4. Sperm cells Highly specialized for their role in fertilization Head: contains the nucleus Acrosome: contains enzymes to digest a passage to the egg Mitochondria: function? Tail: for movement

5. Formation of sperm • The testes • produce sperm • the hormone testosterone • Sperm do not complete their development at body temp (37°C) • So the testes are outside of the body in the scrotum

6. Spermatogenesis • The testis is packed with tightly coiled seminiferous tubules • Sperm production, or spermatogenesis, takes place inside the tubules • Spermatogenesis begins in germ line cells on the outside of the tubule

7. Spermatogenesis • Germ line cells in the seminiferous tubules undergo meiosis to form sperm • Are sperm haploid or diploid? • They are released into the seminiferous tubule • Adult males produce several hundred million sperm each day

8. Meiosis: review Germ line cell is diploid DNA is replicated Two cell divisions Meiosis I and Meiosis II. The result? 4 haploid daughter cells 2n Produces gametes n

9. Spermatogenesis • Sperm cells are made in the testis • Develop motility in the epididymis • Delivered to the vas deferens • When sperm is ejaculated, it travels from the vas deferens to the urethra

10. Spermatogenesis • Sperm leave the penis in a fluid called semen • Various glands (seminal vesicle, prostate gland and Cowper’s gland) add fluids which help nourish the sperm

11. Sperm delivery system • The penis contains 3 long cylinders of spongy tissue • It is designed to inflate • Nerve impulses cause the blood vessels leading into this tissue to expand • Blood collects in the spongy tissue and causes the penis to become erect and rigid • Continued stimulation is required for ejaculation

12. Hormones control the male reproductive system • The pituitary gland secretes 2 hormones, FSH and LH • FSH stimulates sperm formation • LH stimulates the testis to produce testosterone FSH LH

13. Testosterone • Develops male sex characteristics • Enlarges the sex organs • Body hair, beard • Voice change • Develops sexual function • Sex drive (libido) • Sperm maturation • Stimulates bone and muscle growth

14. The female reproductive system • Designed to • Produce 1 egg each month • Prepare the uterus for implantation of the fertilized egg Ovulation

15. Anatomy of the female reproductive system • The eggs, or ova, mature in the ovaries • The fallopian tubestransport egg to the uterus • The uterus is lined with epithelial tissue called the endometrium • the surface of the endometrium is shed during menstruation • the uterus narrows to a muscular “neck” called the cervix • The vagina leads from the uterus to the external genitalia

16. The Female Reproductive Cycle • The female reproductive cycle is actually two cycles in one: • The ovarian cycle • Growth and release of 1 egg each month • Coordinated by FSH and LH • The menstrual cycle • prepares the uterus for possible implantation of an embryo. • Coordinated by estrogens and progesterone

17. The ovarian cycle • Eggs develop from cells called oocytes • During each reproductive cycle, one (usually) of the oocytes matures • Only ~400 oocytes mature and are ovulated in a woman’s lifetime Ovary and Fallopian tube

18. Ovulation –only 1 egg matures each month • Ovulation: the mature follicle discharges the egg • The egg is swept up into the Fallopian tube • where fertilization may occur Ovary and Fallopian tube

19. FSH and LH coordinate the ovarian cycle FSH • FSH stimulates the growth and maturation of a follicle • The follicle cells secrete estrogen into the bloodstream

20. FSH and LH coordinate the ovarian cycle FSH FSH andLH • Estrogen levels peak at 12 days • this causes LH levels to surge • and stimulates ovulation at 14 days • The mature follicle bursts and releases an egg

21. FSH and LH coordinate the ovarian cycle FSH FSH andLH LH • LH (luteinizing hormone)stimulates • Formation of the corpus luteum • Secretion of progesterone and estrogens • If the egg is not fertilized, the corpus luteum breaks down

22. The uterine (menstrual) cycle • Rising levels of progesterone and estrogens promote thickening of the endometrium • When the corpus luteum breaks down  drop in levels of these hormones • Endometrium begins to shed – menstruation

23. 28_24a Pituitary FSH LH Ovary Uterus Time

24. FSH, LH Female reproductive cycle X Negative feedback Estrogen Progesterone Menstrual cycle Ovarian cycle

25. Estrogens have several important functions • Develop and maintain female reproductive structures, secondary sex characteristics, and the breasts • Increase protein synthesis • Preserve bone density • Regulate synthesis of cholesterol by liver

26. Embryonic Development

27. It all starts with fertilization • Copulation releases hundreds of millions of sperm into the vagina • Only a few hundred survive the trip to the egg • Only one will fertilize it.

28. The process of fertilization Onlyone sperm reaches the egg Figure 26.13

29. The egg’s journey • Fertilization takes place in the Fallopian tube • The fertilized egg begins mitosis – a series of cell divisions called cleavage • It eventually forms a ball of cells called a blastocyst which implants in the lining of the uterus

30. The blastocyst • Implantation occurs at day 7 • The inner cell mass forms the developing embryo • These are pluripotentstem cells – they give rise to all types of cells in the body • The outer cell layer (trophoblast) becomes part of the placenta • Provides nutrients and oxygen to the embryo

31. What prevents menstruation? • The implanted embryo secretes a hormone, human chorionic gonadotropin (hCG) • hCG tells the corpus luteum to continue secreting estrogen and progesterone • This prevents menstruation • Because hCG comes from the embryo and not from the mother, pregnancy tests measure hCG

32. Stages of early development • Fertilization • Cleavage • Implantation of the blastocyst (day 7) • Neural tube forms (days 16-25) • the first tissue to develop • Organogenesis (4 weeks) • Formation of body organs • From embryo to fetus 1 4:18 http://www.youtube.com/watch?v=0xvJ-NNuR6M

33. Fetal Development: organogenesis • The process of forming body organs begins in the 4th week of pregnancy • This is a crucial time • Most spontaneous abortions (or miscarriages) occur during this period • Alcohol use during pregnancy is one of the leading causes of birth defects, producing fetal alcohol syndrome Human embryo at 4 weeks

34. A month-old embryo • Brain and spinal cord have begun to take shape • Four stumpy limb buds • A short tail • Looks like most month-old vertebrate embryos

35. Programmed cell death –a key developmental process • Certain tissues produced during embryonic development are destroyed– apoptosis • Cells in the developing hands and feet are killed, separating the fingers and toes

36. Fetal Development: the first trimester • Development is essentially complete at the end of the third month of pregnancy • All the major organs are present • Arms and legs begin to move • The developing human is now referred to as a fetus Human fetus at 3 months 2 From embryo to fetus 3:20 http://www.youtube.com/watch?v=aw5v6_5GaLQ&NR=1

37. Ultrasound imaging • By the end of the 1st trimester, the sex of the fetus can be determined by an ultrasound exam • An ultrasound image is produced when high-frequency sound waves are bounced off the fetus

38. Fetal Development • The second trimester is a time of growth • During the 4th month, the bones enlarge • Mother can feel baby kicking • By the end of month 6, the fetus can survive outside the uterus with special medical care Human fetus at 4 months

39. Fetal Development • The third trimester is a period of rapid growth • The weight of the fetus doubles • Brain and lungs complete development • The growing fetus is fed by the placenta which passes nutrients from the mother’s bloodstream into the fetal blood supply • But maternal and fetal blood don’t mix

40. The placenta • An organ unique to mammals • Allows close contact between the bloodstreams of the developing fetus and mother • The placenta supplies the fetus with oxygen and nutrients, and allows fetal waste to be disposed of via the mother’s kidneys • Placenta also synthesizes hormones required to maintain pregnancy Oxygen, nutrients and hormones to baby Wastes and CO2 from baby

41. Childbirth • The birth of a child is brought about by a series of strong, rhythmic contractions of the uterus called labor • Labor is induced by a strong surge of 3 hormones

42. Three stages of labor • Dilation of the cervix • Opens to a width of 10 cm (4 inches) • Delivery of the infant • Strong uterine contractions • Delivery of the placenta • The “afterbirth”

43. Family planning Preventing pregnancy

44. Birth control • Contraception methods differ in their effectiveness • Most effective • Sterilization (vasectomy, tubal ligation) • IUD • Implant • Least effective • Withdrawal • Spermicides • See Birth control effectiveness chart on Planned Parenthood website • http://www.plannedparenthood.org/health-topics/birth-control//birth-control-effectiveness-chart-22710.htm

45. Sterilization tubal ligation vasectomy

46. What is an IUD? • Intrauterine device • IUDs are small, "T-shaped" devices inserted into a woman's uterus to prevent pregnancy. • Effective for at least 5 years • How Does an IUD Work? • Copper affects the motility of sperm, preventing fertilization. • Also alters the lining of the uterus and prevents the fertilized egg from implanting in the uterus.

47. The implant • A matchstick-sized rod that is inserted in the upper arm • Releases the hormone progestin and prevents ovulation • It protects against pregnancy for up to 3 years.

48. Other methods that use hormones to prevent ovulation • Hormone methods • Birth control Shot, Pill, Ring, Patch • Breast feeding • The birth control shot contains progestin • The pill, ring and patch contain both estrogen and progestin. • The hormone methods work by preventing ovulation

49. FSH LH Negative feedback How do these hormones prevent ovulation? • Female sex hormones coordinate the reproductive cycle • FSH and LH  Ovulation • Estrogen and progesterone  prepare the uterine lining for implantation • Birth control pills contain estrogen and progestin • Turn off production of FSH and LH • Prevent ovulation Estrogen Progesterone

50. Breastfeeding • While a woman is continuously breastfeeding, her body does not make hormones that are necessary for ovulation • Less than 1 out of 100 women who practice continuous breastfeeding perfectly will become pregnant. • Using breastfeeding as birth control can be effective for 6 months