What do Sertoli cells and Leydig cells do?
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
What are the key phases of the menstrual (ovarian) cycle?
- Follicular phase
- Midcycle
- Luteal phase
What do regulatory hormones/cells do in males?
LH - Stimulates testosterone production
FSH + Testosterone - Support Sertoli cell function
Sertoli cells - Support Spermatogenesis
What do regulatory hormones/cells do in females?
FSH - Stimulates some development of ovarian follices (it’s in the name) and 17Beta-Oestradiol synthesis
LH - Stimulates Progesterone production
Steroids - Regulate uterine endometrium
How do hormonal levels fluctuate over the menstrual cycle?
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)
How do hormones feedback to the HPG axis?
Follicular: oestradiol -ve fb to anterior pituitary + hypothalamus
Midcycle: oestradiol +ve fb to anterior pituitary + hypothalamus
Luteal: progesterone -ve fb to anterior pituitary + hypothalamus
What are the key phases of the endometrial cycle? How are they linked to the menstrual cycle?
Menses - follicular phase
Proliferative
Secretory - corresponds to luteal phase
Describe gametogenesis in males
- Primordial germ cells (44X/Y)
- Spermatogonium (44X/Y)
Mitosis - Primary spermatocyte (44X/Y)
Meiosis 1 - Secondary spermatocyte (22X/22Y)
Meiosis 2 - Spermatids (22X/22Y)
- Spermatozoa (22X/22Y)
Into lumen –> epididymis –> vas deferns –> urethra
Describe gametogenesis in females
- Primordial germ cell
- 2n oogonium
- 2n primary ooctye
- 2n secondary oocyte + 2n 1st PB
—— stops at first meiosis until puberty
In meiotic arrest metaphase II
How does fertilisation occur?
- Sperm deposited in female system near cervix during sexual intercourse
- Cervical mucus normally hostile to sperm –> physical barrier; changes midcycle so sperm can enter uterus
- Sperm passes the uterus into fallopian tube to ampulla:
- survival of fittest (few days) - Capacitation - essential prep bf sperm meets oocyte
- Egg meets sperm - fusion (within 24h post-ov)
- Acrosome reaction: penetration of zona pellucida + coronal cells
- Calcium flux
- Resumption of meiosis - maternal chromosomes separate to form female pronucleus, release of 2nd PB
- Alignment of maternal + paternal chromosomes to generate zygote
- Cortical reaction: hardening of zona pellucida to prevent more sperm fusing w/zygote + inactivation of sperm receptors
- Initiation of mitotic divisions in embryo
What drives ovulation?
LH peak in midcycle phase
How does an oocyte mature?
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
How long do follicles take to grow?
Over about 3 months
NOT monthly
