Menstrual Physiology Flashcards
How many phases in ovarian cycle and what are they?
2 (3 if pregnancy included)
- Follicular phase
- Luteal phase
What happens in follicular phase?
Primordial follicles arrested at prophase I
- FSH from anterior pituitary stimulates a number of primordial cells to begin maturation
- As granulosa cells mature they increase in size and number and secrete oestrogens which drive cycle
-After 13ish days dominant follicle develops and in creases in size: LH surge leads to ovulation
What happens to left over follicle in luteal phase?
Partially collapses and forms corpus luteum
What does corpus luteum do?
Secretes oestrogen and progesterone
-If fertilization doesn’t occur the corpus luteum regresses so progesterone secretion falls, endometrial lining is shed and cycle can begin again
If fertilization occurs?
HCG production from trophoblast maintains corpus luteum formation until 10-12 weeks of gestation
-By which time placenta will be making sufficient oestrogen and progesterone to support self
Average uterine cycle length?
28 days
Day 1-3 called?
Menstrual phase
What happens in menstrual phase?
Withdrawal of hormones result in shedding of endometrial lining
Day 1-14 is what phase?
Proliferative phase
What happens in proliferative phase?
Responsible for variation in length of someone’s phase
-Begins at menstruation, there is oestrogen driven growth of endometrial glands and stroma
Day 15-28 known as?
Secretory phase
What happens in secretory phase?
Progesterone induced glandular secretory activity, decidualization, then endometrial apoptosis and subsequent menstruation
What is decidualization?
Changes to cells for preparation of pregnancy
What stimulates FSH and LH release and from where?
Pulses of GnRH at about 2 hour intervals
-From anterior pituitary
What does LH stimulate?
Theca cells to produce androgens
What does FSH stimulate?
Growth of ovarian follicles and associated rise in FSH via negative feedback
What happens when oestrogen reaches a ~certain~ concentration level?
Exerts positive feedback resulting in an increase in FSH and LH surge
What hormone causes ovulation and regulates formation of corpus luteum?
LH
What does corpus luteum do?
Secretes progesterone and oestrogen so FSH and LH fall due to negative feedback on GnRH pulsatility
Fall in progesterone results in?
Increased GnRH and FSH (cycle can begin again)
Granulosa cells produce?
Oestrogens & progesterone
Thecal cells produce?
Ovarian androgens when stimulated by
LH
