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Reproduction

Learn about the male and female reproductive systems and the role of hormones in sexual reproduction. Understand the process of fertilization, the functions of the male and female reproductive organs, and the hormonal control of the menstrual cycle.

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Reproduction

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  1. Reproduction Core Topic 6.6

  2. Sexual reproduction – requires union of egg and sperm (fertilization) • Male produces sperm, female produces eggs • Sex cells are made in the gonads (ovaries and testes) • Eggs and sperm are haploid (made by meiosis) so that when they unite, the diploid number is restored

  3. Male Reproductive System • Main organ: testes • Located at the base of the abdominal cavity • Develop from same embryonic tissue as female ovaries

  4. Testes have 2 functional components: • Seminiferous tubules– produces sperm; only functional at slightly lower body temp. • Scrotal sac approximately 1.5 C cooler that abdomen • Epididymis – coiled tube where sperm travel from seminiferous tubules; lie on top of testes; sperm stored here and acquire ability to swim • Interstitial cells– secrete male sex hormone testosterone

  5. Vas deferens– 2 long ducts that carry sperm from epididymis to urethra (common duct for passage of sperm and urine) • Urethra passes through penis and empties to outside • As sperm passes through the vas deferens, sperm is mixed with seminal fluids to form semen • Seminal fluids are secreted by seminal vesicles, prostate gland, and Cowper’s gland (bulbourethral gland) • Seminal fluid functions as: • Vehicle for transport of sperm • Lubricates passages where sperm pass • Acts as a buffer fluid to protect sperm from acids in female reproductive tract • Contains fructose for source of energy

  6. 6.6.4 List three roles of testosterone in males. • Hormonal control of male reproduction: • During embryonic development – small amounts of testosterone cause differentiation of male structures • Testosterone levels remain low until onset of puberty (no sperm production) • At puberty, testes begin to release testosterone which begins production of sperm • After puberty, secondary sex characteristics result from testosterone (beard, pubic hair, underarm hair, deepening of voice, development of larger and stronger muscles) • In adults, it maintains the sex drive (libido)

  7. Female Reproductive System • Ovaries – located in abdominal cavity; held in place by ligaments; produce gametes and sex hormones • At time of birth, ovaries already contain hundreds of oocytes (primordial egg cells) • Each oocyte is enclosed in a follicle – each month when egg ripens, follicle grows and fills with fluid and bulges on surface of ovary, ovulation occurs and egg is released into body cavity

  8. Follicles in ovary Ovulation

  9. Egg is taken up by oviducts (Fallopian tubes) • Fertilization must occur in upper third of oviduct for baby to result • Egg finishes maturation (completes meiosis II) with penetration of sperm and nuclei fuse

  10. Oviducts empty directly into uterus • Uterus: • About the size of a fist • Lies in lower portion of abdomen behind bladder • Muscular sac with thick walls of smooth muscle, lined with mucous, contains many blood vessels • Location where fertilized egg implants and develops

  11. 6.6.1 Draw and label diagram of the adult male and female reproductive systems. Bartholin’s gland Labia minora Labia majora

  12. 6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormones), estrogen and progesterone. • Hormonal control of female reproductive system • At puberty, FSH and LH (made by pituitary gland) stimulate the ovaries to produce estrogen and progesterone. This starts menstrual cycle. • Estrogen stimulates development of secondary sex characteristics (pubic and underarm hair, broadening of pelvis, development of breasts, distribution of fat, changes in voice) http://www.youtube.com/watch?v=WGJsrGmWeKE Ovulation & MC

  13. 6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormones), estrogen and progesterone. • Human Menstrual Cycle • Averages every 28 days • 1st day of menstruation is day one of cycle • Days 1-5: lining is sloughed off (lining is thin) http://course.zju.edu.cn/532/study/theory/2/Genital%20system/Menstrual%20cycle.swf MSNBC Menstrual Cycle

  14. 6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormones), estrogen and progesterone. • Events during the 1st half of the cycle (approximately days 1-14): • Pituitary releases FSH stimulating the maturation of several follicles (only 1 will complete maturation); also stimulates ovaries (follicle) to secrete estrogen • Estrogen stimulates thickening of uterine lining • Estrogen stimulates the release of an abrupt surge of LH (by pituitary) almost midway through the cycle; LH surge is followed by ovulation (around the middle of the cycle – about day 14) • Estrogen inhibits the pituitary from releasing more FSH (negative feedback)

  15. 6.6.2 Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinizing hormones), estrogen and progesterone. • Events during the 2nd half of the cycle (days 15-28) • After ovulation, LH stimulates ruptured follicle to form the corpus luteum; continues to release estrogen and also progesterone • Progesterone promotes continued buildup and support of the uterine lining (also inhibits production of FSH and LH – negative feedback) • If no fertilization occurs , corpus luteum degenerates, progesterone levels drop, lining is shed and cycle starts over

  16. 6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and thickening of the endometrium. Ovarian and Uterine Cycle http://www.sumanasinc.com/webcontent/animations/content/ovarianuterine.html

  17. Hormonal control of pregnancy • Once fertilized, egg immediately becomes impermeable to other sperm cells – membrane changes consistency • Fertilized egg forms the zygote • Cell division occurs as zygote travels down oviduct to uterus and it implants in the wall of the uterus 8-10 days after fertilization

  18. After implantation – fertilized egg forms embryo, umbilical cord (vessels connect baby and mother), and placenta (formed from embryonic and uterine tissues; blood systems of baby and mother come in close contact but never actually mix; exchange occurs between circulatory systems)

  19. Fertilized egg produces human chorionic gonadotropin (HCG) which keeps corpus luteum in place, which continues to produce progesterone to sustain pregnancy • Eventually placenta takes over production of estrogen and progesterone to maintain uterine lining

  20. 5 weeks ~1 cm long 14 weeks ~6 cm long 20 weeks ~30 cm at end of 24 weeks

  21. 6.6.5 Outline the process of in vitro fertilization (IVF). • In vitro Fertilization (IVF) • Normal fertilization takes place in the oviduct • Sometimes a couple may be infertile – unable to conceive a baby • In vitrofertilization involves fertilization of eggs in the laboratory in a test tube https://www.youtube.com/watch?v=jsJ6dPmfLwA IVF

  22. 6.6.6 Discuss the ethical issues associated with IVF.

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