The Menstrual Cycle Flashcards
What are the aims of the menstrual cycle?
- Selection of a single oocyte
- Correct number of chromosomes in eggs
- Regular spontaneous ovulation
- Cyclical changes in the vagina, cervix and Fallopian tube
- Preparation of the uterus
What are the different factors that control the menstrual cycle?
- Hypothalamus
- Anterior pituitary
- Ovary
- Oestrogen
- Progesterone
In what condition does the GnRH has to be for the menstrual cycle?
GnRH has to be in pulsatile
What are the different stages of the menstrual cycle?
- Day 1: first day of menses
- Follicular phase
- Ovulation
- Luteal phase
What happens in the Follicular phase?
- Growth of the Antral follicles up to ovulation ->
- dominated by oestradiol productions from Antral follicles
When does Ovulation occur during the cycle?
During day 14 of cycle
What happens in the Luteal phase of the menstrual cycle?
- Formatiom of the corpus luteum from remaining cells of follicles ->
- Dominated by progesterone production from corpus luteum
What occurs at the end of the 28 day cycle?
Menstruation occurs at the end if there’s no pregnancy
State what the corpus luteum is?
Remnant of the follicle that becomes the corpus luteum
What type of response is the Luteal phase?
Negative feedback by progesterone
What type of response is the Follicular phase?
Variable response
1. Release/removal of negative feedback
2. Negative feedback is reinstated
3. Switch from negative to positive feedback
What happens at the late Luteal early follicular stage?
- Progesterone declines
- Selectively raises FSH
- Leads to an inter cycle rise
What happens at the mid follicular stage?
- E2 increases
- Negative feedback occurs
- FSH falls
What happens at the mid cycle phase?
- 2 days of E2 >300 pmol
- Positive feedback occurs
- Causes an LH surge
What happens at the mid Luteal stage?
- High progesterone
- Causes negative feedback to occur
- Low LH/FSH
- Progesterone overcomes E2
Describe the inter cycle rise in FSH
The inter cycle rise and fall in FSH is very important because it allows selection of a single follicle which will go onto become the dominant follicle that will ovulate
How is Follicle selection achieved?
- Raised FSH present a “window” of opportunity to recruit Antral follicles that are at the right stage to continue growth