Unit 4.2 Day 27 Reproductive Ovaries

gonads compound glands

holocrine

endocrine

gonads: holocrine

produce gametes (ova)

while in utero

gonads: endocrine

produce estrogens + progestins

not until sexual maturation

oogenesis

generation of germ cells

paused as primary oocyte

primary follicle makeup

primary oocyte + follicle cells

ovarian cycle

strongly linked to precise levels of endo. H

avg. cycles every 28 days

phases

• follicular phase

• ovulation

• luteal phase

follicular phase

at maturity, follicle develops

theca layer

granulosa layer

ovarian cycle follicular phase: theca layer

stim. by LH

activates GPCR →→ cAMP → PKA

prod. testosterone from cholesterol

ovarian cycle follicle phase: granulosa layer

stim. by FSH

convert testosterone to estradiol (E2) w/ aromatase

• stims. cont. oogenesis + follicular devel.

• + other fx outside ovarian cycle

ovarian cycle follicular phase results

mature follicle (gaafian follicle)

ovarian cycle: ovulation

follicle swells + bursts

release oocyte = ovulation

ovarian cycle luteal phase: follicular cells leftover

corpus luteum

corpus luteum produces

estrogens + progestin

maintains pregnancy until placenta takes over

• fertilized: implanted

• not fertilized: degenerates into corpus albicans

sex steroids overview

do not play reproductive roles until puberty

estrogens source

granulosa cells of follicle + corpus luteum

estrogens function in ovary

follicular development (oogenesis)

estrogens function in uterus

thickens uterine lining

estrogens mechanism of action

estradiol - classic genomic pathway

estradiol mechanism of action

nuclear receptors: ERa, ERb

binds DNA at estrogen response element (ERE)

impacts recruitment of RNA polymerase II + other transc.-initiation complexes

progestins source

corpus luteum

progestin function in ovary

NONE

progestins function in uterus

maintain uterine lining + pregnancy

progestins mechanism of action

progesterone: membrane-mediated

progesterone mechanism of action

GPCRs (g-protein-coupled receptors)

• PRa

• PRb

• stims. Gai

  • reduces cAMP levels

  • leads to enhanced germinal vesicle breakdown (GVDB)

  • 1st stage meiosis

• Gby

  • → PI3k/Akt pathway

  • stims. GVDB

hormonal regulation overview

HPG axis

GnRH

LH

FSH

luteotropic complex

gonadotropin releasing hormone (GnRH) overview

secretory neurons

CNS integrate signals to reg. GnRH pulse generator

• changes in freq, not ampl.

• signals like photoperiod, nutrition, stress, etc

FSH hormonal regulation

stims granulose cells: androgens (T) → E2

stims follicle growth

prod follicle fluid (antrum)

E2 prod

LH hormonal regulation

stim theca cells to steroidogenesis (C27→C19 androgens)

disrupt follicle → ovulate

corpus lute formation (luteinizing action)

• E2 + progestin prod.

luteotropic complex hormonal regulation

group of H responsible for endocrine reg. (not just single stim/regulator)

PRL, estrogens, human chorionic gonadotropin (hCG), placental lactogen (hPL)

stim. corpus luteum to prod. E2 + progesterone

follicular phase days

1-14

follicular phase overview

hypothal. stim to secrete GnRH in response to low estrogen levels

FSH + LH secreted from ant. pit.

granulosa + theca cells begin to mult. around developing oocyte

release estrogen + inhibin

• neg. feedback to hypothal. + ant. pit.

ovulation overview

high enough levels of estrogen pos.