2. folliculogenesis and oogenesis Flashcards
1
Q
female internal sex organs and their functions
A
- ovary: female gonad: oogenesis, hormone production
- fallopian tube: fertilization
- uterus: emb. and fetal development
- vagina: spermatozoa or menstrual flow
2
Q
oogenesis timing
A
- oogonia are no longer present in females after 5th month of fetal development
- oocytes finish meiosis with fertilization
- primary oocyte present at birth arrested in prophase of meiosis one
- continues hrs before ovulation: secondary oocyte arrested at metaphase of meiosis II
- minutes after fertilisation: completion of meiosis II and discarded second polar body
3
Q
differences from spermatogenesis
A
- genesis
- quantity of gametes produced
- quality of cells: cell hypertrophy, cell differentiation
4
Q
specialisation of the egg cell
A
- for independent development
- large nutrient reserves and an elaborate coat (ZP)
- zona pellucida: specialised form of extracellular matrix protecting the egg from mechanical damage and species barrier to sperm
5
Q
PCG and oogonia
A
- PCGs migrate to the developing ovary: oogonia
- diploid oogonia undergo several mitotic divisions this providing ovary with large supply of future eggs (ova)
- when oogonia begin the first meiotic division, they are called primary oocytes
6
Q
zona pellucida
A
- 3 filamentous glycoproteins: ZP1, ZP2,ZP3
- 2,3 form constitute dimeric filaments joined by ZP1 bridges
- promote acrosome reaction (ZP3)
7
Q
oocyte development
A
- in follicles
- primary oocytes are dormant
- a single layered squamous capsule of epithelial support cells (follicle cells) tightly encloses oocyte
- follicles subsequently degenerate at birth to puberty
8
Q
what is a follicle
A
- in the ovary a follicle is formed by the oocyte (gamete) and its support cells (somatic cells)
- oocyte niche
- two cell types develop together surrounded by a basal lamina
- hormones regulate the development of mature (antral) follicles supported by extensive vascularization
9
Q
primordial follicle recruitment
A
- by paracrine mechanisms
- paracrine communication between oocyte, its associated graulosa cells, adjacent interstitial cells and surrounding follicles combine to control
- largely mediated by secreted growth factors
10
Q
folliculogenesis
A
- accompanies the maturation of oocytes
- physical barriers to cell-to-cell communication established
1. theca cells
2. granulosa cells: connected to oocyte
3. oocyte
4. zona pellucida
5. transzonal projections
6. mural granulosa cells
7. cumulus cells
11
Q
primordial follicle
A
- primordial follicle: one primary oocyte surrounded by a single layer of flattened follicular cells
- about 5-12 resume development each month to become primary
12
Q
primary follicles
A
- grown by increasing the GC layers
- stage 1
- not under hormonal control
- follicular cells become cubic
- a glycoprotein coat is present at the border between follicular cells and the oocyte by both cell types: ZP
- follicular cells (granulose cells, GC) proliferate and form multiple layers: granulosa
- slowly grow until stage 4-5: 4-5 layers of follicular cells
13
Q
secondary follicles
A
- characterised by a cavity
- develops into a graafian follicle
14
Q
graafian follicle
A
- identified by a large atrium and corona radiata that surround the antrum
- still contains primary oocyte surrounded by corona radiata
- CR cells remain attached through ZP after ovulation
- oocyte does not increase in size
15
Q
follicular atresia
A
- a competitive process determines the loss of majority of oocytes
- follicles fail to develop
- only a few with antrum proceed
- follicles become progressively more sensitive to stimulating effects of FSH: those most acutely are favoured
- oocyte with most LH receptors on granulose cells can survive low FSH concentrations
- ovulation induced by LH surge 72h after emergence of ovulatory follicle
- millions of oocytes but only 3-4000 ovulated
- initial recruitment - cyclic recruitment - selection - dominance
- some apoptosis
