Chapter 37: Reproductive Cycles Flashcards
Discuss when we see the follicular phase of the menstrual cycle
Follicular phase: Begins with the onset of menses (first day of the cycle) and ends on the day of the LH surge.
Alright, so what happens when conception does not occur? Why do we see cramping during this time?
Conception does not occur –> involution of the corpus luteum –> decline in progesterone and estrogen –> menstruation (3-7 days, getting rid of clots during this time)
Prostaglandins and menstrual blood cause contractions of uterus vasculature and musculature, which in turn cause ischemia and uterine cramping.
What causes cessation of the menstrual period?
Rising estrogen levels in the early follicular phase induce endometrial healing which leads to cessation of menstruation
Alright so estrogen and estrodiol are rising to heal up the uterus and stop the crappy part of the cycle, the period
What happens as this estrogen level goes up?
Estradiol levels rise, causing a decline in the FSH. LH stays low until about mid-phase since estrogen has a positive feedback on it, and as estrogen rises, LH comes back.
Several follicles begin the maturation process, but only one becomes the dominant follicle (has the greatest number of granulosa cells and FSH receptors, and the highest estradiol production).
Alright, maturing follicles sounds a lot like we are approaching ovulation. I get that estrogen went up to heal up the uterus, but that seems a little too convenient. Why did the estrogen levels rise?
Estradiol levels rise in the follicular phase because at the end of the luteal phase, estradiol, progesterone, and LH are at their lowest levels, and in response, FSH begins to rise at the end of the luteal phase, causing an increase in estradiol levels.
So as estrogen starts to come back, what hormone starts to rise again?
LH. Positive feedback from estrogen on LH
I hope you remember that the LH surge is what causes ovulation, but where the hell does this surge come from?
LH is fed positively by estradiol, and this dominant follicle is DOMINANT because it’s secreting buckets of this stuff. LH wakes up and comes out in a fury. By day 11-13, LH is so high (been rising for last 36 hours), ovulation occurs.
What is mittelschmerz?
Some women feel this rupture, a twinge of pain called “mittelschmerz”
Right after ovulation, support systems pick up. Describe them:
Theca and granulosa cells undergo change and start producing protective progesterone. Meiosis of the primary follicle occurs after ovulation and release of first polar body. Oocyte then arrests in metaphase of meiosis II and stays that way until fertilization. Follicle turned to corpus luteum when oocyte is gone.
When and what is the luteal phase?
Luteal phase begins on the day of the LH surge and ends with the onset of menses. It’s during this phase that we switch from predominantly estrogen to predominantly progesterone, changing the machinery of the theca and granulosa cells to make P instead of E, called leutinization.
Has negative feedback effect on pituitary, decreasing FSH and LH. Meanwhile, corpus luteum is making estradiol in parallel to the amount of progesterone being made.
Discuss progesterone production for menstrual cycle
Progesterone production begins 24 hours before ovulation with maximum amount 3-4 days after ovulation. Corpeus luterum lasts for 9-11 days, if no fertilization, it involutes, causing a sharp drop in progesterone, causing FSH to rise again and repeat the cycle. If fertilized, chorionic gonadotropin from the zygote keeps the corpus luteum alive for 6-7 weeks. The placenta takes over around weeks 9-10.
What is corpus albicans?
Corpus luteum is yellow when active, and when it is done after a few months, it is a white streak within the ovary called a corpus albicans
What is happening to the uterus with estrogen?
During folicular phase when the estrogen levels are highest, the endometrium proliferates and elongates, reaching its peak just before ovulation. But this proliferated mass of tissue doesn’t make anything. Progesterone changes that
After estrogen makes the uterus big and bulky, what does progesterone do?
Progesterone turns the uterus into a secreting one, differentiating the components of the endometrium, making the stroma more loose and edematous and blood vessels become thickened and twisted.
Endometrial glands that were streaight and tubular in proliferation become tortuous with secretory material in the lumen. But without continuous
progesterone, this active layer sloughs off.
What happens to the uterus if we do not have progesterone?
Important note. If no progesterone cycle, estrogen just keeps going, and the proliferation never stops, giving you a thick straight uterus, which will die in sections randomly instead of all at once (anovulatory bleeding)
