2.2 - the menstrual cycle: lecture - fertilisation occured

Question 1

what happens at the end of the cycle if fertilisation has occurred?

Answer 1

syncytiotrophoblast (outer cell mass, week 2 of 2’s) produces human chorionic gonadotrophin (hCG)

Question 2

what is the action of human chorionic gonadotrophin (hCG)?

Answer 2

exerts a luteinising effect

hCG = LH (effect), corpus luteum will survive under hCG like it does under LH

Question 3

when is hCG able to be redundant?

Answer 3

until placenta able to produce enough steroids to support HPO axis throughout pregnancy

Question 4

how does corpus luteum support pregnancy?

Answer 4

CL is supported by placental hCG

CL produces steroid hormones to support the pregnancy

Question 5

what are the 2 stages of ovarian cycle?

Answer 5

follicular and luteal

Question 6

what are the 3 stages of uterine cycle?

Answer 6

1. menses (menstruation) - within follicular
2. proliferative phase (proliferation of lining that has been shed) - (in line with follicular)
3. secretory phase (corpus luteum secrete) - in line with luteal

Question 7

why does corpus luteum breakdown? which phase?

Answer 7

oestrogen and progesterone levels fall within luteal phase
contraction of artery leads to corpus luteum becoming ischaemic
(this will be the menstrual phase)

Question 8

when does ovulation occur?

Answer 8

on day 14

Question 9

what is the actions of oestrogen (gonadal steroid) within the follicular phase?

Answer 9

fallopian tube development
thickening of endometrium
growth + motility of myometrium (SM of uterus, surrounding endometrium - thickens)
thin, alkaline cervical mucus (promote fertilisation)
vaginal changes
changes in skin, hair, metabolism

Question 10

what is the action of progesterone within the luteal phase?

Answer 10

further thickening of endometrium into secretory form
thickening of myometrium, but reduction of motility (don’t want myometrium to contract)
thick, acid cervical mucus
changes in mammary tissue
increased body temperature
metabolic changes
electrolyte changes

Question 11

how often does menstruation occur?

Answer 11

menstruation occurs on a month cycle throughout reproductive life, unless interrupted by a pregnancy

Question 12

what is the normal duration of menstruation?

Answer 12

21-35 days

28 days is not fixed

Question 13

what are variations in a cycle duration due to?

Answer 13

due to variation in the length of the FOLLICULAR phase

Question 14

how long is the luteal phase?

Answer 14

strictly controlled as 14 +/- 2 days

corpus luteum has a defined 14 day life span

Question 15

what are the factors which affect the menstrual cycle?

Answer 15

1. physiological factors: pregnancy, lactation
2. emotional stress
3. low body weight