gonads

Question 1

how long is the menstrual cycle

Answer 1

usually 28 days

Question 2

when does the menstrual cycle begin

Answer 2

taken to begin on first day of menstruation

Question 3

what is the important reproductive event in the menstrual cycle

Answer 3

ovulation

Question 4

when does ovulation occur and what is it

Answer 4

release of ripe ovum around day 14

Question 5

what are the 2 cycles within the menstrual cycle

Answer 5

ovarian cycle (ovaries) and endometrial cycle (uterus)

Question 6

stages of ovarian cycle

Answer 6

follicular phase → (ovulation) → luteal phase

Question 7

stages of endometrial cycle

Answer 7

proliferative phase → secretory phase

Question 8

ovarian cycle: what hormone acts in the follicular phase

Answer 8

17B-oestradiol

Question 9

ovarian cycle: what does 17B-oestradiol do in the follicular phase

Answer 9

acts on uterus and has proliferative (positive feedback) effect: lining gets thicker, inducing more 17B-oestradiol and progesterone receptors

Question 10

ovarian cycle: what hormones act in the luteal phase

Answer 10

progesterone and 17B-oestradiol

Question 11

ovarian cycle: what does progesterone do in the luteal phase

Answer 11

act on uterus and has secretory effect: suitable for implantation

Question 12

what hormone triggers ovulation

Answer 12

LH

Question 13

oestrogen and progesterone levels in early follicular phase

Answer 13

low so little negative feedback

Question 14

LH and FSH levels in early follicular phase and effect on 17B-oestradiol levels

Answer 14

pre-antral follicle show some development without FSH or LH, but high levels of FSH and LH cause cohort of follicles to develop and mature under regulation of FSH, increasing production of 17B-oestradiol

Question 15

how does an increase in LH and FSH levels cause an increase in 17B-oestradiol levels

Answer 15

LH binds to LH receptors on oocytes → stimulates steroidogenesis to produce androgens → aromatase diffuses into granulosa cells and causes expression of FSH receptors → FSH binds and activates aromatase → causes synthesis of androgens to 17B-oestradiol

Question 16

changes to gland blood supply and endometrium thickness in early follicular phase

Answer 16

glands increase blood supply, enlarge and coil, and the endometrium thickens to provide opportunity for maturation

Question 17

what stimulates LH and FSH levels to be high

Answer 17

high GnRH levels

Question 18

17B-oestradiol level in early-mid follicular phase and effect

Answer 18

one follicle is more sensitive to FSH so is bigger and starts producing more 17B-oestradiol, increasing 17B-oestradiol levels

Question 19

local autocrine positive feedback in early-mid follicular phase

Answer 19

increase in 17B-oestradiol stimulates production of more granulosa cells, which therefore increases 17B-oestradiol levels further

Question 20

effect on LH and FSH of 17B-oestradiol in proliferative phase, and effect on follicles

Answer 20

negative feedback so LH and FSH levels begin to decrease, killing all follicles except largest, dominant one

Question 21

what does the dominant follicle become

Answer 21

Graafian follicle

Question 22

properties of Graafian follicle in mid follicular phase

Answer 22

largest follicle no longer requiring FSH to develop and proliferate; keeps growing and producing large amounts of 17B-oestradiol

Question 23

17B-oestradiol leveles in late follicular phase and effect on GnRH/LH secretion

Answer 23

extremely high 17B-oestradiol levels from Graffian follicle causes positive feedback on GnRH/LH secretion

Question 24

effect of GnRH/LH secretion in late follicular phase

Answer 24

triggers a gonadotrophin (LH and FSH) surge; LH surge triggers ovulation

Question 25

in luteal phase what does the follicle become, how is this achieved, and what does it susequently produce

Answer 25

follicle becomes corpus luteum as granulosa cells enlarge and are invaded by blood vessels; starts producing progesterone and 17B-oestrodiol

Question 26

progesterone function

Answer 26

prepares endometrium for implantation; becomes secretory lining

Question 27

progesterone effect on basal body temperature

Answer 27

slight increase

Question 28

effect of progesterone, 17B-oestradiol and inhibin on LH and FSH levels in secretory phase

Answer 28

exert negative feedback on LH and FSH, suppressing their levels

Question 29

what do glands secrete in secretory phase, and what happens to the mucosa

Answer 29

glycogen and other nutrients; mucosa engorged with blood

Question 30

if fertilisation doesn’t occur, what happens to the corpus luteum and the subsequent effect on 17B-oestrodiol and progesterone levels

Answer 30

luteolysis (degradation of corpus luteum) and subsequently 17B-oestrodiol and progesterone levels decline

Question 31

effect of decrease in 17B-oestrodiol and progesterone levels

Answer 31

negative feedback effect lessened so FSH and LH rise again so endometrium becomes narcotic and is shed in maturation, and cycle restarts