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Female resproduction (Phases of egg cell (Antral cells (Produce steroids…
Female resproduction
Phases of egg cell
Preantral phase
(85 DAYS)
- Oogonia (follicle formation)
- Primordial (follicle activation)
- Primary (follicle growth)
- Secondary (follicle growth)
- LH and FSH receptors appear between 2-3
Antral phase
(8-12 DAYS)
- Tertiary: recruitment, selection and dominance (follicle growth)
- Preovulatory
-
Follicular development does get to a point when further follicular devlopment does require external support
- Right hormones not there: follicles: atresia
Antral cells
-
- Only cells of theca interna bind LH
- Only granulosa cells bind FSH
- Theca cells synthesise androgens acetate and cholesterol (LH) (not oest or prog (yet))
- Granulosa cells cant form androgens but can convert androgens to oestrogens (stimulated by FSH)
FSH and LH production
-
GnRH
- GnRH released by neurones in hypothalamus
- Oestrogen high, less GnRH
- Oestrogen low, more GnRH
ANTERIOR PITUITARY
FSH
- Gonadotrophin: gonadotrophin cells anterior pituitary
- Act upon granulosa cells: produce oestrogen
- Oestrogen stimulates proliferation of GC (grow and more fluid)
- Surge of circulating oestrogen from most advanced follicles
- Stimulate LH receptors on granulosa cells
LH
- Produced by gonadotrophin cells of anterior pituitary in response to GnRH
- Acts upon theca cells of ovary to produce androgen
- LH receptors on maturing ovarian follicle further promote oestrogen production
- LH surge precedes ovulation
-
Ovulation
- Expanding antral follicles will die unless brief surge of LH coiincides with appearance of LH receptors on outer GC
If LH surge occurs when both GC cells and theca cells can bind LH, the follicle will make it to preoviulatory stage (25mm)
- Rapid change in siz, bulge at ovarian surface
- Connective tissue breaks down and follcile ruptures
- Follicular fluid released and out flows oocyte surrounded by cumulus cells
Structure of Ovary
- Develops from mesonephros and gonadal ridge
- Bilateral (432)
- Attached to anterior abdominal wall by suspensory ligament of ovary and to uterus by ovarian ligament
- Contains stroma, oocytes, follicular and granulosa cells
Changes
Fetal
- 7mil primary oocytes devlop in fetus to 2 mil at birth
- Follicular devlopment arrested at prophase 1 of meiosis
Menarche
- Follicular maturation restarted
Perimenopause
- Low levels of follicles recruited
- Less responsive to LH and FSH
-
-
- Relatively few oocytes release
- Release is not in continuous stream: episodic: OVULATION
- Pre-ovulation: Oestrogen dominance
- Post- ovulation: progesteron dominance
Cyclic release has effect on cyclicity of body
Genital tract of female:
- Trasnport gametes to site of fertilisation (oestrogenic)
- Prepare site of implantation of conceptus (progestogenic)