1. Primordial follicle (primary oocyte)
formed prenatally
diploid, prophase I
resumes meiosis on individual basis when ovulated
granulosa cells undergo hypertrophy and proliferate under influence of local growth factors
2. Unilaminar Primary Follicle
characterized by cuboidal granulosa
3. Multilaminar Primary Follicle
zona pellicuda: glycoproteins, barrier to autoimmunity
FSH-R-deficient females show a block in folliculogenesis before antral follicle formation
4. Secondary/Antral Follicle
develops under FSH control (10-20 formed per cycle)
granulosa cells secrete follicular liquor to antrum (similar to plasma - polysaccharides, steroid binding proteins, inhibin, follistatin (inhibits FSH))
cumuls oophorus starts to form - see next
characterized by antrum
5. Mature Graffian Follicle
granulosa = avascular
theca = vascular
cumulusoophorus = ova + zona pellucida
corona radiata: layer of granulosa cells immediately around ova
theca: highly vascular, secrete androgens, which are converted to estrogens by granulosa cells (more and more as grows)
the mature graffian follicle is the largest follicle
increased estrogen --> decreased FSH --> increased LH --> ovulation
LH induces completion of first meiotic division - forms first polar body and secondary oocyte
then second meiotic division --> stops at metaphase (diploid)
Follicular Cycle
6. Corpus Hemorrhagicus
ovulation occurs
walls of follicle collapse, ruptures capillaries in theca interna
7. Corpus Luteum
granulosa cells secrete follistatin and inhibin --> decrease FSH
LH stimulates transformation into luteal cells
granulosa luteal cells - secrete progesterone, convert androgens to estrogen
theca luteal cells - secrete progesterone and androgens
corpus luteum gets larger until 9th day after ovulation --> more progesterone secreted --> decreased LH by negative feedback
if no pregnancy, decreased LH --> corpus luteum degenerates
if pregnancy, corpus luteum continues to enlarge (via HCG)
8. Corpus Albicans
corpus luteum invaded by fibroblasts, type I collagen fibers from scar
scar slowly contracts
9. Atretic Follicle
degenerating follicle, forms small connective tissue scar
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