Menstrual Cycle

[blazinfury]

I have several questions about the menstrual cycle and would appreciate some clarification. Thanks.

 

1. Upon birth, a female child is born with primary oocytes. At puberty, primary ooctyes become secondary oocytes. Now it is at menstruation that each of the secondary oocytes are released from the follicle and the whole process occurs. My quest is whether all of the primary oocytes are converted into secondary oocytes at puberty or it is only that primary oocytes start to be converted at each menstrual cycle? I think that the latter is more correct and if so, that means that a female has both secondary and primary oocytes before mensturation. Is there a time or ratio that details when a primary oocyte becomes a secondary oocyte-- is it 3 hrs b/f menstruation?

 

2. You only form a blastula if 2ndary oocyte is fertilized, correct? So if the secondary oocyte is not fertilized, it remains trapped in Meiosis II since it requires a sperm to tell it to finish Meiosis II. Since it takes around 10 days for the blastula to implant if egg is fertilized, but when it is not, then by Day 23,the corpus luteum starts to degrade since there is no hCG to maintain it, correct? You also have no progresterone to maintain the lining and so there is sloughing off. If that is the case, then how does the body rid itself of the secondary oocyte and where is it by Day 23-- abdominal cavity still?

 

3. Is there no more corpus luteum by the second trimester since the placenta takes over and makes estrogen and progesterone?

 

4. Before ovulation, there is a small amount of Estrogen that is secreted by the mature follicle that stimulates contraction and negative feedback to GnRH and prevents release of LH and FSH. By ovulation, you have a buildup of Estrogen and so the high levels of Estrogen go to stimulate LH and FSH release and thus you have the spike at ovulation? Is it the increased estrogen levels that stimulate the release of LH?

 

If that is correct, then when someone is on the pill (which contains low levels of estrogen and progesterone), how does the pill prevent the increase in Estrogen levels from the mature follicle? Also how does a person on the pill menstruate but not ovulate-- is it that the follicle never pops and so the secondary oocyte is not released, but the whole follicle dies by Day 23 with the secondary oocyte within it?

 

Thank you.