reproductive physiology Flashcards
what reproductive hormone is released by the hypothalamus?
gonadotrophin releasing hormone (GnRH)
how is GnRH released in females compared to males?
males- pulses in a constant frequency
females- pulses vary - every 1-2 hours in early follicular phase slowly decreasing to every 4 hours during luteal phase
what is GnRH responsible for?
release of FSH and LH from the anterior pituitary
how is GnRH release regulated?
kisspeptin neurons have receptors for oestrogen and progesterone which regulate GnRH pulsatility
what phase causes variation in menstrual cycle length?
follicular phase- typically 14 +/- 7 days, luteal phase is more constant (14 days)
describe menstrual cycle in terms of hormones
-FSH stimulates growth of ovarian follicles (associated with an increase in oestrogen levels)
-Rising oestrogen levels in turn exert negative feedback regulation (level of hypothalamus and pituitary) to lower FSH levels (temporarily)
-Once oestrogen reaches a certain concentration it exerts positive feedback regulation resulting in an increase in FSH levels and the LH ‘surge’
-LH surge eventually leads to ovulation and regulates the formation of the corpus luteum and progesterone production and secretion
-Increasing progesterone decrease LH secretion by influencing GnRH pulsatility
what hormones cause the endometrium to thicken and shed?
oestrogen causes thickening, progesterone causes it to become secretory tissue
describe folliculogenesis
once a follicle reaches a certain size it becomes gonadotrophin dependant. if it coincides with rise in FSH in early follicular phase number will continue to grow and 1 will be selected for ovulation.
how long is the LH surge before ovulation?
34-36 hours
how is the corpus luteum formed?
under influence of LH
granulosa and theca cells transform into luteal cells
increase in progesterone production (stimulated by LH which causes angiogenesis and enzymes that convert cholesterol to progesterone)
what are the functions of oestrogen?
Increase the thickness of the vaginal wall
Regulate the LH surge
Reduce vaginal pH through increase in lactic acid production
Decrease viscosity of cervical mucus to facilitate sperm penetration
what are the functions of progesterone?
Pro-gestation (maintain pregnancy)
-Maintains the thickness of the endometrium
-Responsible for infertile thick mucus (prevent sperm transport and help prevent infection)
-Relaxes the myometrium (smooth muscle). Functional progesterone withdrawal thought to regulate parturition (birth)
describe testicular organisation
Extratubular compartment (interstitial and intravascular component)
Intratubular compartment (basal and a adluminal compartment): Sertoli cells and germ cells (different stages of development)
where does spermatogenesis occur?
seminiferous tubules
what is the function of testosterone during spermatogenesis?
Maintains the integrity of the blood-testes barrier
Release of mature spermatozoa from Sertoli cells by influencing peritubular myoid cells
