Endo-Repro L17 Female 1 Flashcards
Cortex comprises of
Follicles in stroma
Follicles consist of
Primary oocyte (egg) plus surrounding granulosa cells
Development of egg
Oogenesis
Stages of Folliculogenesis:
- Primordial
- Primary (or antral)
- Secondary (or antral)
- Tertiary (or pre-ovulatory)
Primordial
diameter
features
Additional
0.1 mm
Primary oocyte (arrested meiosis) surrounded by single layer of flattened granulosa cells
Transition is a spontaneous event
Primary (Pre-antral)
diameter
features
Additional
0.5-4 mm Increase in size of oocyte. Proliferation of granulosa cells. Formation of zona pellucida
Requires FSH and LH to convert to next stage
Secondary (antral)
diameter
features
Additional
5-20 mm
Formation of antrum and cumuls oophorus
Only after puberty
Tertiary (pre-ovulatory)
Additional
20-25mm
Primary oocyte resumes meiosis – increase in volume of follicular cluid.
Formation of stigma
Occurred after LH surge
Primordial follicles: Stage
Most primitive
Primordial follicles:Consists of
A primary oocyte surround by flattened granulosa cells.
Primordial follicles:Oocytes are formed by
Mitotic divisions of primordial germ cells and oogonia, granulosa cells derive from stroma
Primordial follicles:Meiosis
Primary oocytes begin meiosis but immediately stop in prophase 1
Primordial follicles:Location
Form a pool around the edge of the cortex.
Follicular atresia
- Much occurs before birth and continues through childhood so by puberty there are about 0.5 million follicles remaining.
- Not altered by pregnancy or the pill
- Accelerated by genetic disorders and chemotherapy
Primary (pre-antral) follicles: Formation is independent of
LH and FSH
Primary (pre-antral) follicles: Involves
- Enlargement of oocyte (still in arrested meiosis)
- Proliferation of granulosa cells
- Formation of zona pellucida
- Formation of theca interna
Secondary (antral) follicles Present in
Antrum
Secondary (antral) follicles Formation needs
LH and FSH
Secondary (antral) follicles Trigger
Slight rise of FSH causes approx. 12 to form at start of each m. cycle
Secondary (antral) follicles Formation involves
- Further proliferation of granulosa cells
- Formation of antrum
- Activation of theca interna
Secondary (antral) folliclesProduces
Oestradiol
Secondary (antral) follicles Majority undergo
Atresia
Theca cell: Stimulation
LH
Theca cell: LH effect causes
Cholesterol via cAMP to be converted into androstenedione testosterone
Theca cell: Output
Androgenic effect if not aromatized in granulosa cell
Granulosa cell: Stimulation
FSH
Granulosa cell: FSH action on the cell
Testosterone converted to estradiol via aromatase
Steroid hormones: Derived from
C27 sterol called cholesterol
Steroid hormones: 3 groups and their functions
- C21 progestogens (e.g. progesterone) → bind progesterone receptors
- C19 Androgens (testosterone) → bind androgen receptor
- C18 Oestrogens (e.g. oestradiol) → bind oestrogen receptor alpha and beta
Follicular selection:
Occurs at
day 9
Tertiary (pre-ovulatory, Graaffian) follicles → Amount per cycle
Only one
Tertiary (pre-ovulatory, Graaffian) follicles →Formation requires
LH surge (LH now targets granulosa cells → due to estrogen
Tertiary (pre-ovulatory, Graaffian) follicles → Involves
- Brief further proliferation of granulosa cells
- Luteinisation of granulosa cells
- Swelling of follicle
- Formation of stigma (site of rupture)
- Resumption of meiosis
Tertiary (pre-ovulatory, Graaffian) follicles →Rupture
About 24hr after onset of LH surge
Tertiary (pre-ovulatory, Graaffian) follicles →Empty follicle forms
Corpus luteum
Tertiary (pre-ovulatory, Graaffian) follicles → Poor LH surge may result in
Luteinisation without ovulation, or an “inadequate” corpus luteum
