Menstruation Flashcards
What is variation in cycle length
Vary greatly
e.g. 20-45 days in adolescence
What % of cycles are 28 days
Only 12%
When are cycles likely to be irregular and anovulatory
Soon after menarche and before menopause
What are the 3 stages on menstruation
Menstrual phase
Proliferative phase
Secretory phase
Menstrual phase
Day 1-5
Proliferative phase
Day 6-14
Secretory phase
Day 15-28
Menstrual phase- what happens
Withdrawal of steroid support of oestrogen and progesterone, so endometrium collapses
Menstrual phase- shedding
Endometrium shed together with blood from ruptured arteries (spinal arteries contract to reduce bleeding)
Menstrual phase average blood loss
Usually between 20-80ml
Median 28ml
Menstrual phase- around 10-15% of women lose more than
80ml
Menstrual phase- What % of women who lose more than 80ml become anaemic
60%
Menstrual phase- 70% of blood loss occurs within the first
48 hours
What is the menstrual flow
Detached endometrial tissue and blood passing through the vagina
Proliferative phase- what happens
Oestrogen from the mature follicle stimulates thickening of endometrium
Glands + spiral arteries form
Proliferative phase- what does oestrogen stimulate
Thickening of endometrium
Synthesis of progesterone receptors on endometrial cells
Secretory phase- what happens
Progesterone from corpus luteum act on endometrium
Secretory phase- what does progesterone stimulate
Enlargement of glands which begin secreting mucus and glycogen in preparation for implantation of the fertilised oocyte
Secretory phase- what happens if fertilisation doesn’t occur
Corpus luteum degenerates
Progesterone levels fall
Endometrium degenerates
Cycle starts again with first day of menstrual flow
