Menstrual Cycle Flashcards
What happens in the follicular phase and what is it dominated by?
Growth of follicles up to ovulation
Dominated by oestradiol
What is the menstrual cycle?
2 phases separated by ovulation (follicular and luteal phase)
Cycle begins on day 1 when shedding of the endometrium occurs
What happens in the luteal phase and what dominates it?
Formation of the corpus luteum from the empty follicle
Dominated by progesterone production from corpus luteum
What happens in late luteal early follicular phase?
Progesterone declines
Selectively raises FSH
Intercycle rise
What happens during the mid follicular phase?
Group of follicles start to grow to get ready in response to FSH
Granulosa cells produce oestrogen
FSH falls once follicle is selected and allowed to grow which produces increased oestrogen
What happens in mid cycle phase?
2 days of oestrogen –> positive feedback = LH surge
What happens in mid luteal phase?
High progesterone = negative feedback –> low LH/FSH
Progesterone overcomes oestradiole
FSH stays very low as you don’t want another egg to be released for fertilisation in case already pregnant
TRUE or FALSE
TRUE
What happens during follicle selection?
Raised FSH presents a window of opportunity
One follicle from the group of antral follicles in the ovary is just at the right stage at the right time.
This follicle becomes the dominant follicle which goes on to ovulate (known as selection)
Oestradiol levels rise (negative feedback on pituitary) –> FSH falls which prevents further follicle growth
Follicular phase gonadotrophins change
FSH falls and LH increases
Dominant follicle acquires LH receptors on granulosa cells
The rest don’t and therefore die
What receptors are found on theca cells?
LH receptors only –> LH drives androgen and progesterone production from theca
What receptors are found on granulosa cells?
FSH receptors first then LH receptors are acquired from mil follicular phase onwards
Which other factors have an input in whether menstruation occurs or not?
Insulin
Leptin –> if not sufficient then cycle doesn’t occur
What does a growing follicle need?
Needs masses of growth factors, nutrients and steroids
What happens during ovulation?
Formation of corpus luteum
Blood flow to follicle increases
Appearance of apex on ovary wall
Local release of proteases
Enzymatic breakdown of the protein of the ovary wall
18 hours after peak of LH a hole appears and ovulation occurs
