Reproductive Physiology

Question 1

What do Sertoli cells and Leydig cells do?

Answer 1

Sertoli cells - big cells in seminferous tubules

• nutritional, hormonal support for spermatogenesis
• respond to FSH
• make inhibin (for -ve fb on HPG axis)

Leydig cells:

• just outside tubules
• LH makes them produce testosterone

Question 2

What are the key phases of the menstrual (ovarian) cycle?

Answer 2

• Follicular phase
• Midcycle
• Luteal phase

Question 3

What do regulatory hormones/cells do in males?

Answer 3

LH - Stimulates testosterone production
FSH + Testosterone - Support Sertoli cell function
Sertoli cells - Support Spermatogenesis

Question 4

What do regulatory hormones/cells do in females?

Answer 4

FSH - Stimulates some development of ovarian follices (it’s in the name) and 17Beta-Oestradiol synthesis
LH - Stimulates Progesterone production
Steroids - Regulate uterine endometrium

Question 5

How do hormonal levels fluctuate over the menstrual cycle?

Answer 5

FSH: steady in follicular, drop + peaks just before ovulation then steadily decreases during luteal, starts to increase back to normal at end of luteal

LH: As with FSH but starts below FSH, peak is larger at ovulation then drops to below FSH

17-B oestradiol: gradually increases during follicular, peaks few days before ovulation, then dips and then increases + dips again in luteal phase

Progesterone: starts off right below oestrogen, stays steady until little peak at ovulation, then dips and increases, overtakes oestrogen near end of luteal phase
(LOOK AT GRAPH)

Question 6

How do hormones feedback to the HPG axis?

Answer 6

Follicular: oestradiol -ve fb to anterior pituitary + hypothalamus

Midcycle: oestradiol +ve fb to anterior pituitary + hypothalamus

Luteal: progesterone -ve fb to anterior pituitary + hypothalamus

Question 7

What are the key phases of the endometrial cycle? How are they linked to the menstrual cycle?

Answer 7

Menses - follicular phase
Proliferative
Secretory - corresponds to luteal phase

Question 8

Describe gametogenesis in males

Answer 8

1. Primordial germ cells (44X/Y)
2. Spermatogonium (44X/Y)
   Mitosis
3. Primary spermatocyte (44X/Y)
   Meiosis 1
4. Secondary spermatocyte (22X/22Y)
   Meiosis 2
5. Spermatids (22X/22Y)
6. Spermatozoa (22X/22Y)
   Into lumen –> epididymis –> vas deferns –> urethra

Question 9

Describe gametogenesis in females

Answer 9

1. Primordial germ cell
2. 2n oogonium
3. 2n primary ooctye
4. 2n secondary oocyte + 2n 1st PB
   —— stops at first meiosis until puberty
   In meiotic arrest metaphase II

Question 10

How does fertilisation occur?

Answer 10

1. Sperm deposited in female system near cervix during sexual intercourse
2. Cervical mucus normally hostile to sperm –> physical barrier; changes midcycle so sperm can enter uterus
3. Sperm passes the uterus into fallopian tube to ampulla:
   - survival of fittest (few days)
4. Capacitation - essential prep bf sperm meets oocyte
5. Egg meets sperm - fusion (within 24h post-ov)
6. Acrosome reaction: penetration of zona pellucida + coronal cells
7. Calcium flux
8. Resumption of meiosis - maternal chromosomes separate to form female pronucleus, release of 2nd PB
9. Alignment of maternal + paternal chromosomes to generate zygote
10. Cortical reaction: hardening of zona pellucida to prevent more sperm fusing w/zygote + inactivation of sperm receptors
11. Initiation of mitotic divisions in embryo

Question 11

What drives ovulation?

Answer 11

LH peak in midcycle phase

Question 12

How does an oocyte mature?

Answer 12

Primordial primary follicle pool
-
Pre antral
Small antral
Large antral
Pre-ovulation follicle
Ruptured follicle - leaves ovary to fallopian tube
Leaves corpus luteum
Breaks down

Question 13

How long do follicles take to grow?

Answer 13

Over about 3 months

NOT monthly