Reproduction and Sex Steroid Axis 2

Question 1

compare the structures of LH and FSH

Answer 1

identical a subunits but specific ß subunits

Question 2

outline male physiology

Answer 2

pulses of GnRH are released from the hypothalamus which stimulate LH and FSH release from the pituitary

Question 3

what does LH do in males

Answer 3

stimulate testosterone production from the Leydig cells of the testes

Question 4

testosterone action

Answer 4

produce appropriate tissue responses: male 2y sexual characteristics, anabolism and maintenance of libido

acts locally within testes to aid spermogenesis

feeds back to hypothalamus/pituitary to inhibit GnRH secretion

Question 5

how does testosterone circulate in body

Answer 5

largely bound to SHBG

Question 6

what does FSH do in males

Answer 6

stimulates the Sertoli cells in the seminiferous tubules to produce mature sperm and inhibins A and B

inhibins feed back to the pituitary to decrease FSH secretion

Question 7

what counteracts inhibin

Answer 7

activin

Question 8

where is GnRH produced

Answer 8

arcuate nucleus in the hypothalamus

Question 9

low and high frequency pulses - LH and FSH

Answer 9

low frequency stimulate FSH, high stimulate LH

Question 10

what does LH do in females

Answer 10

stimulates ovarian androgen production by the ovarian theca cells

Question 11

what does FSH do in females

Answer 11

stimulates follicular development and aromatase activity in ovarian granulosa cells

stimulates the release of inhibin from ovarian stromal cells, which inhibits FSH. Counteracted by activin

Question 12

aromatase activity

Answer 12

enzyme that converts androgen to oestrogen

Question 13

mean duration of menstrual cycle

Answer 13

28 days

Question 14

average duration of menses

Answer 14

3-8 days

Question 15

when does ovulation normally occur

Answer 15

mid cycle - day 14

Question 16

normal estimated blood loss in menstruation

Answer 16

30ml

Question 17

follicular growth

Answer 17

• begins when oestrogen levels are low - provides feedback for FSH and LH secretion which stimulates follicles to develop
• one leading follicle develops by day 8-10
• granulosa cells around the egg enlarge and release oestrogen - this negatively feedbacks to the pituitary causing it to produce less FSH, meaning there is only enough to stimualte one follicle

Question 18

when in the menstrual cycle does ovulation occur

Answer 18

• enlarged granulosa cells causes oestrogen levels to rise, this makes the pituitary more responsive to GnRH - LH surge
• after the LH peak the oocyte is released: collagen wall of the follicle is digested and it ruptures releasing the ova into the Fallopian tubes
• where it waits to be fertilise by une sperm

Question 19

luteal function phase

Answer 19

secretory phase that starts after ovulation

beigns with the formation of the corpus luteum from remaining granulosa cells

this releases oestradiol and progesterone by the action of 3ß-HSD

Question 20

when is peak progesterone production noticed

Answer 20

one week after ovulation takes place

Question 21

what happens to the CL in the absence of pregnancy

Answer 21

luteolysis - progesterone levels drop, uterine lining detaches and menstruation begins

In pregnancy, the CL continues to release oestradiol and progesterone maximizing the chance of implantation into the endometrium.

Question 22

what is in the discharge in menstruation

Answer 22

tissue, blood and unfertilized egg

Question 23

how does an ovulation predictor kit work

Answer 23

detects the LH surge, 36 hours before ovulation

Question 24

what effect does progesterone have on temperature

Answer 24

thermogenic - increases basal body temperature during ovulation

Question 25

what type of cycles are suggestive of ovulation

Answer 25

regular, confirmed by midluteal (day 21) serum progesterone (>30nmol/L on 2 samples)

Question 26

IP (suspensory ligament)

Answer 26

attaches the ovary to the pelvic side wall

Question 27

where are the follicles found in the ovary

Answer 27

in the cortex

Question 28

what happens in the uterus in response to oestrogen

Answer 28

made more hospital to sperm - lining of the endometrium thickens

if there is a lack of hCG and progesterone, it sloughs off

Question 29

which cells facilitate the progression of germ cells to spermatozoa

Answer 29

Sertoli cells (FSH)

Question 30

what is a spermatogonium

Answer 30

undifferentiated male germ cell

Question 31

describe the development of spermatozoa

Answer 31