02.2 Menstrual Cycle Flashcards
In the menstrual cycle which part is the follicular phase?
The beginning immediately after menses and before ovulation
What phase begins after ovulation?
The luteal phase
Which is the first hormone to begin rising and why?
FSH due to low levels of Oestrogen and Progesterone not negatively feeding back on it
How does FSH act?
Binds on granulosa cells
Follicular development continues
What hormones does the follicle secrete?
Inhibin
Oestrogen
After the follicle begins secreting inhibin and oestrogen, which hormone is next affected and why is it the only hormone that increases?
LH
Oestrogen feeds back on the HPG axis however inhibin selectively inhibits FSH secretion
Following the LH surge, production of which hormone begins?
Progesterone
Post ovulation what does the corpus luteum secrete?
Oestrogen and Progesterone (and inhibin)
What happens to LH levels after ovulation?
Decrease due to the presence of progesterone
What does the reduction of LH post-ovulation lead to?
Regression of the corpus luteum and a fall in gonadal horomes (cycle resets)
UNLESS fertilisation occurs and hCG luteinises the corpus luteum
What produces hCG?
Syncytiotrophoblast
What are the actions of oestrogen?
Increase fallopian tube motility
Endometrial thickening
Growth of myometrium
Thin, alkaline cervical mucus (good for sperm)
What are the actions of progesterone?
Further thickening of endometrium and myometrium
Makes endometrium secrete more mucus (good for implantation)
Thick, acidic cervical mucus (spermicidal)
Changes in mammary tissue
Increased body temperature
How long does the luteal phase last?
14 days
How much does the luteal phase vary?
Not very much
+/- 2 days
