Menstrual cycle

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Menstrual cycle in women

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Menstrual cycle

  1. 1. Menstrual cycle
  2. 2. Onset of menstruation Day 1 Day 10 4 8 12 16 20 24 28Menstruation
  3. 3. Key events in ovarian cycle Day 1 LH 1. Follicular growth0 4 8 12 16 20 24 28 Oestradiol OvulationMenstruation
  4. 4. LH surge Day 1 LH Day 1 Days before Days after Follicular phase Luteal phase0 4 8 12 16 20 24 28 OvulationMenstruation
  5. 5. Key events in ovarian cycle LH 2. Ovulation Day 1 1. Follicular growth0 4 8 12 16 20 24 28 Oestradiol OvulationMenstruation
  6. 6. When does ovulation occur? The timing of ovulation varies with the length of a womans menstrual cycle. In the average 28 day menstrual cycle, the LH surge usually occurs between cycle days 11-13 and ovulation follows about 36-48 hours later, on or close to cycle day 14.
  7. 7. Key events in ovarian cycle LH 2. Ovulation Day 1 1. Follicular growth 3. Luteal function0 4 8 12 16 20 24 28 Oestradiol Oestradiol (& Progesterone) OvulationMenstruation
  8. 8. Key events in ovarian cycle LH 2. Ovulation Day 1 1. Follicular growth 3. Luteal function 4. Luteal regression0 4 8 12 16 20 24 28 Oestradiol Oestradiol (& Progesterone) OvulationMenstruation
  9. 9. The follicle is the fundamental element of the ovary Cumulus Oocyte cells Antrum Zonapellucida
  10. 10. What controlfollicular growth? Hypothalamus GnRH Pituitary Steroid LH feedback FSH Ovary Estradiol Reproductive tract
  11. 11. What controlfollicular growth? ?????Gonadotropinindependent Ovulation 4 8 12 16 20 24 28 0 Oestradiol Menstruation As each follicle grows, it produces increasing amt of Estradiol
  12. 12. The follicle is the fundamental element of the ovary LH Androgens are converted (aromatized) to estradiol by granulosa cells Androgens FSH Oestradiol Inhibin
  13. 13. HypothalamusIncreasing GnRH –ve feedback - Pituitarymechanism Inhibin suppress Increasing amount of LH ↓FSH FSH estradiol + Ovary Estradiol + Reproductive tract
  14. 14. FSH As the follicle grow, FSH level fall due to the –ve feedback mechanism Estradiol0 4 8 12 16 20 24 28
  15. 15. Why is only one selected & become dominant ?Many follicles atthe start of the cycle Ovulation 4 8 12 16 20 24 28 0 Menstruation
  16. 16. Hypothalamus Increasing GnRH –ve feedback - Pituitary mechanism Inhibin suppress Oestradiol ↓FSH FSH + Small folicle Ovary Large foliclevery dependent independent on on FSH FSH Growth factor estradiol X Dominant + + follicle
  17. 17. FSH secretion suppressed FSH Estradiol Dominant follicle (s) can survive Insufficient FSH to keep smaller follicle going to become atretic0 4 8 12 16 20 24 28
  18. 18. What causes ovulation ? Oestradiol What effects does it have ? What causes LH surge ?0 4 8 12 16 20 24 28
  19. 19. HypothalamusFor most of thecycle negative feedback GnRH mechanism - operates Pituitary ↓ LH & FSH LH Inhibited by FSH estradiol Estradiol Ovary
  20. 20. Hypothalamus ↑GnRH But, with highlevel of estradiol GnRH maintained for + ↑Sensitivity to GnRH long enough Pituitary + LH surge Estradiol Ovary
  21. 21. How does the LH surge affects the follicle ?About 36 h between LH surge & oocyte release…..
  22. 22. Oocyte Loosening of the cumulus cellsEnzyme induction in the follicle wall Oocyte
  23. 23. Transformation of ruptured follicle into corpus luteumMature follicle become Corpus luteum Steroid secretion changes Progesterone + Estradiol
  24. 24. What maintains the CL ? Follicular phase Luteal phase Estradiol domination Progesterone domination Why does the CL degenerates at the end of the cycle ? 0 4 8 12 16 20 24 28 Ovulation
  25. 25. What maintains the CL ? Hypothalamus ~8 h between LH pulses GnRH Pituitary LH very low levels CL CL very sensitive Progesterone + to LH E2
  26. 26. What maintains the CL ? Hypothalamus - GnRH Steroid negative feedback keeps Pituitary LH & FSH level relatively low - LH (low levels in CL + luteal phase) Progesterone + E2 CL very sensitive Reproductive to LH tract etc
  27. 27. Towards the end Hypothalamusof the cycle, thesensitivity to LH reduces GnRH Pituitary The low level of LH are insufficient to keeps the CL LH going CL degenerates Progesterone + E2
  28. 28. Hypothalamus GnRH As CL degenerates Pituitary steroid negativefeedback reduces ↑ FSH + LH Progesterone +of folicles A new wave stimulated by rising FSH & LH E2
  29. 29. Other changes in the cycle 1. Outer muscles layer the myometrium 3. Inner glandular layer mucusa the endometrium
  30. 30. Uterine changes in menstrual cycle Endometrial depth Estradiol cause an ↑ in More secretion from the thickness gland, hence the term (the proliferative phase) secretory phase0 4 8 12 16 20 24 28 Opt time for Ovulation implantation
  31. 31. Time course of menstruationOnset of menstruationis rapidProbably, 95% womenhave a total blood loss ofless than 60 mlThis blood loss canrepresent as a significantloss of iron (leading toanemia)- especially inwomen on marginal diet
  32. 32. Menstruation….Why ?In preparation of pregnancy, the human uterinestromal cells go through complex changes and thestromal cells terminal differentiateIf implantation and pregnancy do not occur, thistissue is lost and the uterus prepares itself again foranother possible pregnancy
  33. 33. Key events in ovarian cycle LH 2. Ovulation Day 1 1. Follicular growth 3. Luteal function 4. Luteal regression0 4 8 12 16 20 24 28 Oestradiol Oestradiol (& Progesterone) OvulationMenstruation
  34. 34. Women fertile window

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