Menstrual Cycle Flashcards
What is the first day of the cycle?
The cycle starts on the 1st day of the period
What day is ovulation on a normal 28 day cycle?
Day 14
What role does FSH have in the menstrual cycle?
Causes an egg to mature in the ovary.
Stimulates the ovaries to secrete oestrogen.
What role does oestrogen have in the menstrual cycle?
It stops FSH being produced - so that only one egg matures in a cycle.
It stimulates the pituitary gland to release the hormone LH
What role does LH have in the menstrual cycle?
The hormone LH causes the mature egg to be released from the ovary.
What is the role of progesterone in the menstrual cycle?
It is produced by the corpus luteum and prepares the uterus for implantation by causing the endometrium to thicken.
It also causes the cervical mucus to thicken to prevent repeat fertilisation.
What happens in the follicular phase?
Day 1-13
As oestrogen and progesterone levels drop the top layer of the endometrium sheds (menstruation)
FSH is produced by the pituitary this stimulates the growth of follicles within the ovaries. As well as producing oestrogen.
The dominant follicle will continue to grow meanwhile the other follicles will breakdown as the FSH levels drop.
The oestrogen stimulates the production of LH.
Note: oestrogen causes FSH levels to drop.
What happens in the ovulatory phase?
Day 14
Surge in LH levels as well as a slight surge in FSH.
Luteinizing hormone stimulates the dominant follicle to bulge from the surface of the ovary and finally rupture, releasing the egg.
The role of FSH here is not understood.
What happens in the luteal phase?
Day 15-28
Occurs after ovulation, the ruptured follicle forms the corpus luteum which produces increasing quantities of progesterone.
Progesterone prepare the uterus for implantation by thickening the endometrium.
Oestrogen levels are also high during the luteal phase and also help to thicken the endometrium.
Progesterone and oestrogen levels also cause milk ducts in the breast to widen causing breast swelling and tenderness.
If fertilisation does not occur the corpus luteum degenerates after 14 days. Progesterone and oestrogen levels drop causing menstruation and the next cycle.
What happens if fertilisation occurs?
The trophoblasts from the fertilised egg produce beta HCG which maintain the corpus luteum which continues to produce progesterone until the growing foetus can produce its own hormones.
