Sexual Reproduction in the Human

1. Sexual Reproduction in the Human (Extended Study)

2. Learning objectives • Outline the stages in the menstrual cycle • Discuss the role of hormones in the menstrual cycle • Discuss the Cause/Prevention/Treatment for fibroids or for endometriosis

3. Menstrual Cycle

4. Hormonal control in the menstrual cycle • Four hormones involved: • FSH (Follicle Stimulating Hormone) • Oestrogen • LH (Luteinising Hormone) • Progesterone • Each hormone causes the production of the hormone following it and inhibits the hormone preceding it

5. FSH – Follicle Stimulating Hormone • Produced by pituitary gland • Produced early in the cycle (days 1-5) • Stimulates a few potential eggs to develop, surrounded by graafian follicles • Only one usually survives • Sometimes used in fertility treatments to stimulate ovaries to produce eggs – often lots of eggs develop. This explains some multiple births • Each graafian folllicle then produces oestrogen

7. Oestrogen • Produced by the graafian follicle in the ovary • Produced from days 5 -14 • Causes the endometrium to develop • Inhibits FSH ensuring no further eggs develop (useful in contraceptive pill) • High levels of oestrogen just before day 14 stimulate release of LH

9. LH - Luteinising Hormone • Produced by the pituitary gland • Produced on day 14 • Causes ovulation • Causes the remains of graafian follicle to develop into corpus luteum • Corpus luteum makes final hormone in the cycle progesterone (along with small amounts of oestrogen)

11. Progesterone • Produced by the Corpus Luteum in the ovary • Produced from days 14-28 • Maintains structure of endometrium • Inhibits FSH to stop further eggs developing • Inhibits LH to stop further ovulation and pregnancies • Prevents contractions of the uterus

14. Learning Check • List the four hormones involved in the menstrual cycle • In each case state where it is produced • Give a function for each hormone

15. Events when pregnancy does not occur

16. Menstrual disorder (Fibroids) • Fibroids are tumours of the uterus • They are the result of the overproduction of cells • They do not invade other tissues and do not spread (benign)

17. Menstrual disorder (Fibroids) • Slow growing and range from the size of a pea to the size of a melon • Common between ages of 35 and 45 • Small fibroids often produce no symptoms • As they enlarge they produce heavy and prolonged menstrual bleeding (this can lead to anaemia, pain, miscarriage or infertility)

18. Cause • Cause is uncertain • May be an abnormal response to oestrogen • Can occur in women taking the contraceptive pill

19. Prevention and treatment • Small fibroids require no treatment just monitoring to check their growth • Large fibroids can be removed by surgery • If many large fibroids are present a Hysterectomy may be necessary. This is where the uterus is removed

20. Menstrual disorder (Endometriosis) • Growth of endometrial cells outside the uterus (often in fallopian tube) • Normally endometrium is shed each month in the menstrual cycle. In endometriosis misplaced endometrium is unable to exit the body • Results in internal bleeding, inflammation of surrounding area and pain • Formation of scar tissue may result • If in the fallopian tube this can interfere with the passage of eggs to the uterus (infertility)

21. Cause • Exact cause remains unknown • Several theories (response to excess oestrogen creation)

22. Prevention and treatment • No known cure • Hysterectomy (removal of uterus) - no guarantee that symptoms will disappear • Medication can be taken to interfere with hormones resulting in a reduction or elimination of menstrual flow

23. Syllabus

24. Depth of treatment • Detailed study of the menstrual cycle and hormonal control

25. Contemporary issues and technology • Menstrual disorders • one example of a menstrual disorder from the following: endometriosis and fibroids • one possible cause, prevention and treatment