Menstrual Cycle Flashcards
When does menstruation start and finish?
Starts at menarche and ends at menopause.
How long is a menstrual cycle?
28 days
Simply, what are the three main phases of the menstrual cycle called?
Follicular/Proliferative Phase - Days 0-13
Ovulation – Day 14
Luteal/Secretory Phase – Days 15-28
Briefly describe female gametogenesis? When are all the eggs formed? What happened at puberty? What happens each month?
Oogonium – Primary oocytes with 1st meiotic division – this is the point at which it is arrested at birth.
At puberty – 1 primary oocyte reaches maturity out of approx. 1000 that are released each month – enlarged primary oocyte – one goes to a secondary oocyte which the other becomes a polar body – the 2nd oocyte matures to a mature ovum which is just waiting to get penetrated by some sperm.
Where do the main hormone all come from? (estrogen, progesterone, FSH, LH, GnRH, inhibin)
FSH and LH are from the pituitary. GnRH is from the hypothalamus. Estrogen, progesterone and inhibin are from the granulosa cells of the follicle and then from the corpus luteum in the second half following ovulation. Androgens are from the thecal cells of the follicle.
Describe what happens in the follicular phase? What are the roles of the hormones involved and what is the feedback mechanism? On what cells are these hormones acting?
Follicular Phase is basically when the follicle growhts, matures and a new layer of endometrium is laid down preparing for pregnancy.
FSH (follicle stimulating hormone) stimulates follicle development…who would have thought. FSH works on the granulosa cells of the follicle to produce estrogen which in turn has a positive feedback on the granulosa cells to produce more estrogen. FSH also has a inhibitory effect on the hypothalamus so reduces production of FSH and LH. Speaking of LH, LH works on the thecal cells to produce androgens which are converted to estrogen in the granulosa cells.
Btw menses is happening in the first 7 days if there was no pregnancy.
Next is ovulation. What happens in this stage? What hormones? On what cells? What effects do these hormones have?
The follicle becomes ripened and releases the oocyte.
At ovulation there is a LH and FSH surge as a result of increased estrogen. Simulatneously there increase in inhibin produced by the granulosa cells as it goes to inhibit FSH and decrease the chance of a new follicle being selected as tribute. #maytheoddsforeverbeinyourfavour. There is small amount of progesterone being released which has slight positive feedback on GnRH and LH.
In this phase the cervix releases abundant, clear, non-viscous mucus which facilitates the entry of sperm. The utuerus focuses on proliferations and increase in progesterone receptors.
Explain what happens in the early to mid luteal phase? Why is this stage called the secretory phase? What happens to all the hormones involved? What effects do these hormones have?
The ruptured follicle transforms into corpus luteum in preparation for pregnancy. #awwwwwwwshiiiiiiiiitttt There is in increase in estrogen but a greater increase in progesterone which acts to maintain the endometrium. The corpus luteum also increases inhibin production which decreases FSH which as before doesn’t allow the selection of new follicles.
The uterus prepares by converting the endometrium to secretory structure to promote implantation. This means that it increases in vascularity as well.
Finally, explain what happens in the late luteal phase? What does this stage depend on?
All depends if someone knocked this bitch up. If she is pregs, maintain feedback and this keeps the hormone levels high in order to maintain the endometrium etc.
If she is not pregs, the corpus luteum dies. This leads to low hormone levels (decreased estrogen and progesterone. Menses then happens which signals the beginning of a new cycle. Increase in FSh and LH once again. Here we go again.
Give a brief summary of the levels of each hormone throughout the menstrual cycle? (estrogen, progesterone, FSH, LH, GnRH, Inhibin)
FH and LH remain low other than when the LH/FSH surge occurs during ovulation due to estrogen
Estrogen is present in the first phase but decreases in the 2nd half
Progesterone is quite low until the 2nd phase when it gets going getting ready for pregs.
Inhibin is used to prevent the secretion of FSH to stimulate a new follicle.
