estrous cycle and folliculogenesis

cow estrous cycle

polyestrous, 21 days

mare estrous cycle

seasonally polyestrous, 21 days

sow estrous cycle

polyestrous, 21 days

ewe estrous cycle

seasonally polyestrous, 17 days

queen estrous cycle

polyestrous, 17 days

bitch estrous cycle

monoestrous, 6 months

HPG axis- female

two control centers→ tonic center + surge center

hormones to discuss: GnRH, LH, FSH, Estradiol, Testosterone, Inhibin

steroidogenesis → Theca interna

layer on the outside of the basement membrane that is directly touching it

produces testosterone

stimulated by LH

steroidogenesis→ granulosa cells

innermost layer of cells

produces estradiol

stimulated primarily by FSH, and also LH depending on follicle stage

StAR protein

steroidogenic acute regulatory protein

transport protein that transfers cholesterol into the inner mitochondrial membrane

this is the rate-limiting step for steroidogenesis

primordial follicles

microscopic and most immature follicle

oocyte is surrounded by single layer of squamous cells

primary follicles

microscopic

oocyte surrounded by a single layer of cuboidal cells

secondary follicles

microscopic

oocyte is surrounded by 2+ layers of cells

antral follicles

no longer microscopic

fluid-filled, atrium

recruitment

a cohort of follicles will be activated and start developing

some follicles will continue to develop while others undergo atresia

dominance

the follicle will/must acquire markers/receptors to continue to develop

depending on the hormonal control, the follicle will either undergo atresia or ovulate

inhibin

inhibits FSH

LH surge results in

ovulation

anestrous

this is without estrous/cyclicity

causes: pregnancy/postpartum, prepubertal, sickness, anorexic/obesity