PDA 1 exam 2 (ovarian and endometrial regulation)

hormonal regulation of female reproductive system

hypothalamus —>pituitary—> gonads

_________GnRH____FSH/LH_____ estrogen

Negative feedback in female reproductive system

negative feedback by estrogen

*exception* day 12 of cycle

• a brief positive feedback from rapidly increasing estrogen stimulates release of LH and FSH

How many eggs in human development?

• ~7 million primordial follicles

• majority undergo atresia

How many eggs at birth?

• ~2 million ova (1/2 are atretic)

• 1million ova undergo 1st meiosis, become arrested in prophase

How many eggs at puberty?

• <3 million ova

• atresia continues

How many mature oocytes during reproductive life?

• ~400-500

• the rest degenerate

atresia

immature ovarian follicles degenerate and are reabsorbed during follicular phase

How many oocytes reach maturity in a normal menstrual cycle?

one

Where does fertilization occur?

middle portion of fallopian tube

What happen to the fertilized egg in the 2nd step of fertilization?

divides and migrates towards uterus

what secretes hCG after impanation in the uterine lining?

blastocyst

hCG stimulates _____ to remain viable and continue secreting ____and _____

• corpus luteum

• progesterone

• estrogen

how many weeks after pregnancy does hCG decrease?

10-12 weeks

during the follicular phase ____secrets estrogen

growing follicle

during luteal phase ____ secretes progesterone and estrogen

corpus luteum

days 1-12 of cycle

dominant follicle secretes high levels of estrogen which stimulation endometrial proliferation

~ day 12 of cycle

brief positive feedback from estrogen stimulates release LH and FSH

~40 hrs after LH and FSH surge

follicle ruptures and ovulation occurs

~day 15-28 of cycle

• corpus luteum secretes progesterone and estrogen

• progesterone- induces endometrium to transition into a secretory phase to prepare to implantation

What happens of fertilization does not occur?

corpus luteum regresses and hormone secretion decreases

E2: Estradiol

• major estrogen in female

• high affinity for estrogen receptor

• made during follicular phase

• converted to E1 and E3 in liver

Thecal cells

LH receptor activation stimulates enzymes to convert cholesterol to androgens

granulosa cells

FSH receptor activation stimulates aromatase activity which converts androgen to estrogens

Physiological effects of estrogen

• breast development

• maturation of ovaries

• endometrial proliferation

• prevent osteoporosis

• increase hepatic proteins and cholesterol

• increase HDL and decrease LDL

physiological effects of progesterone

• 0.6 F rise

• crucial for maintaining pregnancy

• increase insulin resistance during pregnancy (diabetes)