week 10 - female reproductive system Flashcards
the oocyte
haploid polar body
zona pellucida: protective jelly like layer
cell surface membrane
chromosomes: ready to undergo second meiotic division after fertilisation
cytoplasm: contains food reserves for developing zygotee
requirement for fertility
The core process relies on the creation and fusion of male and female gametes
- Production normal sperm (spermatozoa)
- Production normal eggs (oocyte, ova)
- Sperm transverses female tract to reach egg
o Time constraint
- Sperm penetrates and fertilise an egg
- Implantation of the embryo into the uterus
- Normal pregnancy
All are under hormonal control
what is oogenesis / folliculogenesis
the production of an ovum
steps of Gametogenesis
same in male and female?
yes
but timing and outcome differ sharply
gametogenesis
the production of gametes from haploid precursor cells
steps in oogenesis
- Oogenesis starts in the embryo (pre-birth)
- Oogenesis is not continuous
o 2 meiotic arrest
o 2 phases where it stop until hormone signal are received - Each diploid cell develops into only 1 haploid cell
- Oogenesis continuous after puberty and stops at menopause
where does Oogenesis start?
(complicated)
occurs pre birth and is not continuous
primordial germ cell
–[migration to gential ridge during early development]–>
oogonium (diploid cells)
—[during embryogenesis]–>
primary oocyte arrested at prophase I = meiosis I pre brith (embryogenesis)
—[ovulation, puberty] = meiosis I resumes—>
secondary oocyte arrested at metaphase II = meiosis II, ovulation, adult
—–[fertalization]—> = meiosis II resumes
female pronucleus + male pronucleus
—[pronuclear fusion]—>
zygote
oogenesis
(simplified)
{pre birth}
oogonia —[mitosis]—>
primary oocyte (two step division process) —[meiosis I, arrest until puberty]—>
PUBERTY - resume MI
{ovulation}
secondary oocyte + 1st polar body —[meiosis II, arrest until fertalisation]—>
FERTILISATION - resume MII
ovumn + 2nd polar body
what is folliculogenesis
development of follicles
folliculogenesis
oocyte must be accompanied by…
some somatic cells
folliculogenesis
Oocyte must be accompanied by some somatic cells:
o Granulosa cells:
Role to nurture germ cells,
Surrounds the oocyte
Produce oestradiol (by release of aromatase) and progesterone (post ovulation)
o Theca cells:
Role to produce hormone (androgen, ‘testosterone’) and progesterone (post ovulation)
Surrounds granulosa cells
Compose the basement membrane of follicle
- This unit is called the follicle (oocyte (meiosis), granulosa cells, theca cells)
- Oocytes develop within follicles and cannot exist without each other
female germ cell number
- Female born with all the eggs they will ever need (undergo a limited number of mitotic division)
Embryo/foetus - Primordia germ cells – 170
- Mid pregnancy – 7, 000, 000
- Limited number of miotic divisions
Birth: 2, 000, 000
Puberty: 400, 000
Menopause: occurs when low ovarian reserve
Only 400-500 will be ovulated.
- Most oocytes undergo atresia (degeneration)
folliculogenesis
steps:
1) primordial follicles
2) primary follicles
3) secondary follicle
4) tertiary follicle
folliculogenesis
steps:
1) primordial follicles
Primary oocyte surrounded by single layer of flattened granulosa
At the time of birth, surviving primary oocytes
folliculogenesis
steps:
2) Primary (preantral) follicle:
Primary oocyte
Granulosa become cuboidal
Theca cell layer and ZP begin to become visible
