Ovarian function Flashcards
1
Q
Think about ova.
What is special about the female reproductive system?
A
- The woman is born with the full quota of ova/follicles that she will ever have
- Around 7 million oocytes at 20 weeks
- 1.2 million at birth
- 4000,000 at puberty
- 400-500 will ovulate
- pool of follicles is never replenished
2
Q
think about eggs
What is the case of attrition? Why is this?
A
- A woman is born with more eggs than she’ll ever need
- This is due to the survival of our species so that we can reproduce
- This is why we have a mestrual cycle
3
Q
What controls part of folliculogenesis (what controls what happens in the ovary and testes)?
A
- The hypothalamic -pituitary axis
- Feedback loop
- Hypothalamus increases GnRH to median eminence
- Leads to the release of LH and FSH from the pituitary gland
-Released to target organs (ovaries/testses) - Leads to release of Estradiol and Progesterone
4
Q
Where is GnrH produced?
A
- In gonadotrophs
5
Q
What is the anatomy of the ovary?
A
- 2 oval shaped glands located on the sides of the uterus
- Atttached to the pelvic sidewall by suspensory ligaments
- Responds to cyclic gonadotropin secretion
6
Q
What are the two main functions of the ovary?
A
- The generation of a mature fertilisable ovum for the preservation of the species
- Production of female sex hormones ( Oestrogen and Progesterone).
7
Q
Where does folliculogenesis take place in the ovary?
A
- The cortex of the ovary (edges near yellow)
- There are primordial follicles (no function until puberty)
- These are then converted into primary follicles if selected
- Then become secondary follicles
- Become fluid filled antrums
- The ovum is surrounded by other layers (theca )
- At ovulation, the Graafian follicle (bulge as it is about to be ovulated) expels the ovum into the fallopian tube
- What’s left is the corpus luteum (secretes a yellow compund known as lutean)
- Happens constantly
8
Q
produces something
What is the function of the corpus luteum?
A
- Produces hormones such as oestrogen and progesterone etc
9
Q
it becomes something else
What happens to the corpus luteum if there is no fertilisation?
A
- It degenerates and becomes absorbed into the wall of the ovary/body (Scar tissue)
- Becomes the corpus albicans (white body)
10
Q
PGCS are first observed in the yolk sac during 4-6 weeks of pregnancy.
What can primordial germ cells give rise to ?
A
- Teratomas = germ cell tumours
- generate from either ovum or sperm
- can become cancerous
- PGCS are germ cells and have the capacity to become any cell type (pluripotent)
- formed by 3 germ cell layers = endoderm , ectoderm and mesoderm)
- develop in either in the ovary,testes , but also nervous system, abdomen
11
Q
What is folliculogenesis?
A
- the maturation/ development of ovarian follicules
- progression of a small no. of primordial follicules into a large graafian follicule
- starts after puberty and with the first menstruation due to an increase in hormone levels
- quite small cells
- only have one layer of cells = grnaulosa cells
- ## Gonadotrophin independent.
12
Q
What are follicles?
A
- The functional unit of the ovary
13
Q
Think about getting the best eggs
What are the stages of folliculogensesis?
A
- Recruitment ; the follicle departs from the resting pool to begin a well-characterised pattern of growth and developement during early follicular phase
- involves several follicles in one ovarian cycle (EVERY MONTH)
- Selection : the sorting of the maturing follicular cohort by atresia (smaller follicles are thought to be less healthy because of less FSH and LH so are killed off). Depends on the follicle size with smaller cells <10mm destined to undergo apoptosis.’
- Dominance - status of the follicle destined to ovulate fiven its presumed key role regulating the size of the ovulatory quota ( inhibits the growth of other follicules).
14
Q
Describe the ovarian cycle?
A
- Primordial follicles start to grow everyday, a cohort will start to grow 3-4 = primary follicles
- Primary follicles : 70 days - small antral ( secondary/tertiary follicles- water filled antrum) follicles (2-5 mm)
- Smalla antral follicles :
- FSH window recruited into ovulatory cycle
- No FSH window = atresia
15
Q
What kind of receptors do follicles have? what do these indicate?
A
- FSH and LH receptors
- The ones with the most FSH receptors are thought to be the best follicles / healthiest
- Response and amount of receptors indicates a healthy follicle
- primary follicles are FSH independent
- When they become secondary follicles, the granulosa cells have FSH receptors on them and begin to respond to them.
- These then become FSH and LH dependent
- A number of follicles will die off due to lack of layers, response and receptors
- The Dominant preovulatory follicle is the one that is ovulated
