Reproduction and the Sex Steroid Axis Flashcards
What is the range in days for a normal menstual cycle?
21-35
Usually ovulation occurs at around day __
Usually ovulation occurs at around day 14
Which hormones stimulate follicle development?
FSH and LH
In the menstrual cycle, why does oestrogen levels increase throughout the follicular phase?
FSH and LH stimulate granulosa cells surrounding the egg
The granulosa cells increase in size and secrete insulin
The follicular phase begins when levels of which hormone are low?
Oestrogen
What is the impact of rising oestrogen levels in the menstrual cycle?
Uterine lining thickens
After ovulation, what does the empty follicle become and which hormone does it secrete?
Corpus luteum
Progesterone
What causes ovulation?
LH surge
What causes rupture of the follicle wall allowing for the release of the egg?
Proteolytic enzymes and prostaglandins
Which two hormones remain fairly low in concentration throughout the follicular phase?
- Oestrogen
- Progesterone
What triggers menstruation?
Lack of hCG
Corpus luteum breakdown and subsequent progesterone decrease
Describe the HPO axis
- Hypothalamus secretes GnRH
- Pituitary secretes FSH/LH
- Ovaries produce oestrodiol, activins and inhibins
Which part of the hypothalamus produces GnRH?
Arcuate nucleus
Which cells does LH act on in order to produce oestrogen?
Theca cells
Which cells does FSH act on in order to produce oestrogen?
Granulosa cells
Which variant of GnRH is responsible for reproductive function?
GnRH1
What are the key functions of FSH?
- Recruits dominant follicle
- Granulosa cell growth
- Activates aromatase activity
What is inhibin and what does it do?
Local peptide in follicular fluid
Negative feedback on pituitary FSH secretion
Enhances local LH-induced androstenedione production
What is activin and what does it do?
Local peptide found in follicular fluid
Stimulates FSH induced oestrogen production
Into which two components are the testes organised cellularly?
- Tubular components
- Interstitial components
What are the two tubular components of the testes?
- Sertoli cells
- Germ cells
What are the two interstitial components of the testes?
- Leydig cells
- Capillaries
Which cells support germ cells within the testes in their development?
Sertoli cells
Which hormone acts on
a) Sertoli cells
b) Germ cells
a) FSH
b) LH
How long does spermatogenesis take?
Roughly 90 days
Which two hormones stimulate spermatogenesis?
FSH and testosterone
(LH stimulates testosterone production)
For which reasons is an oocyte much larger than a sperm cells?
- Yolk proteins
- Ribosomes
- t-RNA
- m-RNA
- Protective chemicals
Where does fertilisation occur?
Ampullary region of the Fallopian tubes
What is capacitation?
The functional maturation of a spermatozoon (mature sperm)
Where does capacitation occur?
Female reproductive tract
What is the zona pelludica?
A glycoprotein layer surrounding the plasma membrane of the oocyte
The acrosomal reaction of the sperm is triggered by what?
Binding to ZP3 (zona pelludica 3)
How is polyspermy prevented?
- Na+ influx in response to sperm binding (fast block)
- Ca2+ release in an indirect response to sperm binding (slow block)
As well as egg activation, which 3 other effects does the sperm have during fertilisation?
- Triggers the egg to complete meiosis
- Triggers a cytoplasmic rearrangement
- Causes a sharp increase in protein synthesis and metabolic activity in general
What does the final stage of fertilisation involve?
Fusion of nuclei to form a zygote
