Female Physiology Flashcards
Maturation of primary oocyte
During puberty, primary oocytes undergo change into secondary oocyte (arrested in metaphase II) –> dependent on the LH surge
- once fertilization occurs –> secondary oocyte undergoes Meiosis II and becomes an ovum
Corpus Luteum
produces progesterone –> silences the ovary and remains patent until either 2nd trimester of pregnancy or it involutes if no fertilization occurs
Summary of Ovarian Follicular Development
- Birth –> all oogonia developed into primary oocytes
- Primary oocytes surrounded by follicular cells = granulosa/thecal cells (primordial follicles)
- Primordial follicles slowly progress to primary follicles
- When follicles exhausted = menopause
- Each cycle, a cohort of follicles recruited and usually one becomes ovulatory follicle
- Recruitment refers to antral follicles stimulated by FSH
- Dominant follicle is largest and produces most hormones
Hypothalamo-Pituitary Ovarian Axis
- Hourly GnRH pulses result in FSH and LH basal secretion
- FSH stimulates follicle development
- FSH/LH promotes estrogen synthesis
- Estrogen feedbacks negatively to hypothalamus and pituitary –> reduces FSH and LH
- Inhibin inhibits FSH secretion, no effect on LH
Feedback of estrogen and secretions
- Feedback relationship between estrogen and secretions reverse when antral follicles are large –> high estrogen induces rapid GnRH pulses and ovulatory surge in LH
- Inhibin levels increase as well to keep FSH in check –> reducing more follicle development
GnRH
polypeptide hormone
- produced in arcuate nucleus of hypothalamus
- pulsatile secretion
- member of Gq –> increased Ca
FSH
follicular growth and estradiol secretion
LH
critical for inducing ovulation
ovulation required for formation of corpus luteum
hCG
1st trimester maintains the corpus luteum -> which keeps progesterone levels high to maintain pregnancy
- later in pregnancy the placenta takes over
FSH, LH, hCG
secretions are cyclical –> essential for normal gonadal response
- serum [ ] increase with removal of ovaries and when ovarian functions decrease
FSH, LH, hCG receptors
Gs protein coupled –> increase cAMP
LH/CH receptors are in thecal cells –> androgen production
FSH receptors are in granulosa cells -> converts androgens to estrogen (estradiol 17beta)
Estrogen receptor
ERalpha –> mediates HPO axis response to estrogen
- SHBG = steroid hormone binding globulin
Menstrual Cycle
- Small increases in LH and FSH lead to follicular growth –> increase synthesis and secretion of ovarian steroids
- High levels of estrogen provoke changes in GnRH to manifest rapid pulses
- Stimulates surge of LH which induces resumption of meiosis
- Ovulation induces luteinization –> corpus luteum
- If no conceptus -> spontaneous luteinolysis
Ovarian Cycle
Estrogen = thickening and proliferation of endometrium Progesterone = halts further growth of endometrium
Maternal recognition of pregnancy
hCG produced by chorion –> maintains/promotes maintenance of corpus luteum
Maintenance of pregnancy
accomplished by placenta
Endocrine control of pregnancy
Shifts from P>E to E>P
Progesterone causes hyperpolarization of myometrial cells –> prevent contractions, inhibits oxytocin receptor synthesis, inhibits ER synthesis
Estrogen causes increase oxytocin receptors, promotes uterine contractility, cervical ripening, increases local PG release from placenta
Prostaglandins
PGF2 and PGE are predominant in reproduction
- involved in rupture of Graafian follicle at ovulation
- primes the uterus for real deal
Oxytocin
secreted from posterior pituitary
- main effects are on uterus and breast during childbirth and lactation
- (+) autoregulation within hypothalamus during labor
Breast Development
Puberty -> development of ductal tree (estrogen, glucocorticoids, and GH dependent)
Pregnancy -> mid-late preg (lobular-alveolar growth), post-partum (copious milk secretion, removal of placenta -> prolactin dependent)
Lactation
Galactopoiesis -> presence of prolactin and removal of milk
Milk Ejection -> oxytocin
Involution -> lack of prolactin or suckling
Folliculogenesis promotion
FSH and LH for women with hypothalamic anovulatory function Clomiphene citrate (estrogen antagonist) for women with endogeneous estrogen activity and normal HPO function
Mimic gonadotropins
Menotropins -> pergonal with hCG given in sequence for ovulation in anovulatory women and production of multiple follicles
Urofolitropin -> metrodin with hCG given in sequence for induction of ovulation of patients with PCOD
Follitropin -> induce follicle development and when coupled with hCG -> induction of ovulation
Clomiphene Citrate
Estrogen antagonist (Selective estrogen receptor modulator)
- blocks ER signaling to hypothalamus and anterior pituitary -> stimulates release of GnRH and gonadotropins
- used as fertility drug to induce ovulation
