3.2 lecture: menstruation

Question 1

what does menstrual cycle involve?

Answer 1

interaction of many endocrine glands + responsive uterus

Question 2

what happens during the menstrual cycle?

Answer 2

interaction of CNS (hypothalamus + AP) WITH ovaries –> results in cyclic and ordered shedding of uterine endometrial lining

Question 3

what are the key hormones in control of menstrual cycle?

Answer 3

GnRH
FSH
LH
oestrogen + progesterone

Question 4

when does the proliferative phase begin?

Answer 4

at the onset of menses until ovulation takes place (shedding of endometrial lining)

Question 5

what takes place during proliferative phase of menstrual cycle?

Answer 5

folliculogenesis

a dominant follicle is selected from a pool of growing follicles that will be destined to ovulate

Question 6

what does the growth of follicles during proliferative phase depend on?

Answer 6

pituitary hormones e.g. FSH

FSH –> granuloSa cells of ovaries

Question 7

what does the growth of follicle lead to?

Answer 7

production of oestrogen from the layers of granulosa cells surrounding the follicle

Question 8

what is oestrogen responsible for?

Answer 8

the proliferation of the endometrial lining of the uterus

progesterone maintains it

Question 9

when does ovulation take place?

Answer 9

peak of follicular growth in response to an LH surge

Question 10

what happens prior to ovulation?

Answer 10

follicles grow to sizes greater than 20mm in average diameter

Question 11

what happens to LH prior to ovulation?

Answer 11

released in positive feedback mechanism from the AP due to prolonged exposure to oestrogen

Question 12

for positive feedback of LH surge to take place, levels of oestrogen must be above which threshold and for how long?

Answer 12

above 200pg/mL for about 50 hours

Question 13

what is required in order for the oocyte to release from the follicle during ovulation?

Answer 13

several proteolytic enzymes and prostaglandins are activated
leading to digestion of follicle wall collagen
(proteolytic enzymes breakdown protein component of follicular wall - egg is released)

Question 14

once an oocyte is released, what is responsible for picking up the egg?

Answer 14

fallopian tube is responsible for picking up the egg and cilia waft egg to ampulla for fertilisation

Question 15

what happens during secretory phase of menstrual cycle?

Answer 15

remaining granulosa cells that were NOT released with oocyte during ovulation enlarges + acquire lutein (carotenoids - yellow colour)

Question 16

what are the granulosa cells remaining in secretory phase called? secreting?

Answer 16

corpus luteum

secreting progesterone

Question 17

when is peak progesterone production?

Answer 17

1 week after ovulation

Question 18

what does the lifespan of corpus luteum depend on?

Answer 18

continued LH support from AP

corpus luteum, hence progesterone production continued

Question 19

if a pregnancy takes place, what maintains the corpus luteum?

Answer 19

hCG (human chorionic gonadotropin)

Question 20

if pregnancy fails to happen, what takes place?

Answer 20

luteolysis takes place

corpus luteum converted to corpus albicans (white scar)

Question 21

what is the normal blood supply to the uterine wall?

Answer 21

uterine artery –> arcuate arteries –> radial arteries –> (myometrium-endometrium junction) –> straight arteries and spiral arteries (endometrium + uterine glands)

Question 22

what happens to cause shedding of endometrial lining?

Answer 22

without progesterone, endometrial lining shrinks + atrophy
This endometrial shrinkage, in turn, “forces” the spiral arteries to coil more and more, and this excessive coiling ends up by restricting the normal blood flow to the endometrial functional layer - therefore sheds

Question 23

what is the main ligament of the uterus?

Answer 23

uterine ligament

Question 24

what is the function of the uterine ligament?

Answer 24

supports pregnancy