Menstrual Cycle Flashcards
What is the follicular and luteal phase?
Follicular phase is from the onset of menstruation to the moment of ovulation (the first 14 days)
Luteal phase is from the moment of ovulation to the start of menstruation (last 2 weeks)
What are oocytes?
A finite number of cells that have the potential to develop into eggs.
What are follicles?
OOCYTES (cells which have the potential to become eggs) surrounded by granulosa cells.
What are the key developmental stages of oocyte development?
Primordial, primary, secondary, Antral (also known as Graafian)
How do follicles mature?
Primary to secondary is always occurring, independent of menstrual cycle, however for secondary follicles they have FSH receptors and to mature they need stimulation from FSH.
What happens to the granulosa cells as the follicles grow?
The granulosa cells secrete increasing amounts of oestrogen (oestradiol), the oestradiol has a negative feedback effect on the pituitary gland reducing FSH and LH produced
What happens in the follicular phase?
The follicles develop, one of the follicles develops further than the others and becomes the dominant follicle, lutenising hormone spikes just before ovulation and causes the dominant follicle to release the ovum from the ovary. The cervical mucus also becomes permeable, allowing sperm to penetrate the cervix at the time of ovulation.
What happens in the luteal phase?
After ovulation, the follicle that released the ovum collapses and becomes the corpus luteum. The corpus luteum secretes high levels of progesterone which maintains the endometrial lining, it also causes the cervical mucus to become thick and no longer penetrable. The corpus luteum also secretes a small amount of oestrogen.
If no fertilisation occurs then the corpus luteum will degenerate and there will no longer be oestrogen and progesterone production, the fall will cause the endometrium to break down and menstruation to occur. The negative feedback on the hypothalamus and pituitary gland from oestrogen and progesterone reduces, allowing the levels of LH and FSH to rise and the cycle to restart.
Where does HCG come from and why is it a measure of pregnancy?
When fertilisation has occurred, the syncytiotrophoblast of the embryo secetes human chorionic gonadotropin which maintains the corpus luteum, without this the corpus luteum will degenerate.
What does menstruation involve?
The superficial and middle layer of the endometrium separating from the basal layer.
