sex steroids and ovulation and cycle shit

what does GnRH do?

signals the anterior pituitary to release FSH and LH

what are the two functions of gonads

production of gametes (ovaries → oocytes, testes → sperm), endocrine functions

what do ovaries produce

estrogen

what do testes produce

androgens (testosterone)

when do these hormones start being secreted

puberty and then through life, men peak in 20s, ovulation starts at puberty and ends at menopause

what ONLY has receptors for sex hormones

gonads

what are testes composed of

seminiferous tubules, surrounded by sertoli cells

what do sertoli cells do

provide nourishments to promote spermtogenesis

what hormone do the sertoli cells have receptors for

FSH

what happens when FSH binds to sertoli cells

spermatogenesis

what hormone do the leydig cells have receptors for

LH

what happens when LH binds to leydig cells

testosterone is produced in high levels (male secondary sex characteristics)

what do leydig cells also have receptors for

androgen on nuclear membrane

what does the testosterone-receptor complex act as

transcription factor

do sertoli cells require testosterone

YES

what do FSH and LH secretion promote

spermatogenesis and release of inhibin from sertoli cells

what does testosterone do for negative feedback

prevent LH release and GnRH release, directly LH and indirectly LH and FSH

where is inhibin released from

anterior pituitary, inhibits FSH release

what does FSH and LH target in women

ovarian follicles in ovary

what two cells are in the ovarian follicles

granulosa and theca cels

what do theca cells do

releases testosterone

what stimulates theca cells

LH

what do granulosa cells do

covert testosterone to estrogen

what does granulosa cells have receptors for

estrogen only

positive feedback loop with estrogen, testosterone, granulosa cells

more testosterone → estrogen, more granulosa cells trigger more conversion

what do granulosa cells secrete

inhibin release inhibits FSH release

what steroid hormone escapes the ovary

estrogen

what does estrogen inhibit

FSH release and GnRH, directly FSH, indirectly FSH and LH

what does this hormone cycling create

the menstrual cycle

ovary layout

follicles, each contains oocyte, layer of granulosa

ovary of born baby

two ovaries with several hundred primary follicles

difference between primary and secondary follicles

many layers of granulosa cells surrounded by theca cells, theca = secondary

when do follicles undergo further development

when LH and FSH are at right levels

when LH and FSH levels are right…

grows larger with more theca and granulosa cells, fluid secreted and cavity forms with fluid, oocyte suspended in stalk of granulosa cells, follicle is graffian follicle, ovary begins to budge

if hormone levels are right after ovary bulging…

secretion of fluid builds osmotic pressure, digestive enzymes on outside of follicle to break down sheath/connective tissue weakening it, pressure ruptures follicles and pushed oocyet and granulosa cells out of ovary into abdominal cavity *ovulation

when oocyte travels through funnel shaped tube with ciliated finger processes

then beat to carry oocyte into oviduct/fallopian tubes, leads to uterus

when does ovulation occur

middle of 28 day cycle

how long can oocyte last in oviduct

one day before it dies of old age or is phagocytosed, sperm must be present this day

how long does sperm live in vagina/cervix

week to 10 days

what happens when fertilization occurs

sperm penetrating egg membrane

what happens to the remnant of the follicle

continues to grow under influence of hormones, mainly (LH), form the corpus luteum

what does corus luteum do

yellow body, is an endocrine organ that secretes estrogen and progesterone

lifespan of corpus luteum

fixed lifespan, 10 days w/o fertilization, wither to scar tissue

how cycle repeats

30 oocytes per day and 900 per month

when are hormones at appropriate levels

puberty, for the first 10 years oocytes die off

what is cause of menopause

depletion of viable oocytes that are capable of cycling

how many oocytes burst per cycle

one

cause of fraternal twins

two oocytes burst instead of one

what does FSH do

stimulate the growth of follicle

does graffian require FSH

yes

at first what level is estrogen secreted at

low levels, FSH and LH flat, little FSH for slow growth of follicles

hormone levels at day 1/2

estrogen low, FSH and LH flat

hormone levels day 5-6

slow growth of follicle causes gradual increase of estrogen concentration

hormone levels day 7-10

estrogen increases, more estrogen,

hormone level day 12

normal negative feedback overpowered, switches to positive feedback, promotes large surge of LH and small surge of FSH (with high estrogen), LH surge

what happens after LH surge

ovulation triggered, follicle ruptured and oocyte expelled (day 14), rapid drop in LH and FSH because still estrogen, estrogen falls after ovulation a bit

what does corpus luteum produce

estrogen and progesterone, replenishes lost ovulation, high levels of progesterone

endometrium lining is sensitive to

estrogen and progesterone

what does estrogen cause endometrium to do

grow in thickness

what is the inner lining of the uterus made of

basal layer of stem cells

what happens day 3-4 (basal)

basal cells proliferate, inner/functional layer thicker responding to estrogen

why is there continual growth of endometrium after first week

zygote needs place to implant and develop

how is blood supplied to endometrium

spiral arteries from basal layer due to estrogen

what causes differentiation of the exocrine glands

progesterone

what do exocrine glands do

secrete glycogen rich mucous into the outer layer of endometrium to provide zygote energy

day 24-25

strong vasoconstrictor, prostaglandin produced, would cut off blood but estrogen prevents

if fertilization occurs day 14

takes 7-10 more days for zygote to show up in uterine cavity implant when endometrium is thickest

if fertilization doesn’t occur

corpus luteum pumping estrogen and progesterone dies

what happens as estrogen and progesterone fall

inhibition of prostaglandin end, vasoconstrictor effects starve endometrium of blood flow, killing tissue via necrosis, bleeding as vasoconstrictor wears off

what does bleeding mark

day 0 of cycle

if fertilization occurs

implanted embryo secrete “chorionic” gonadotropin, extra embryonic membrane formed by embryo

what does chorion do

endocrine organ that secretes a chorionic gonadotropin hormone similar to LH

how does chorionic gonadotropin effect ovarian follicle

extending corpus luteum lifespan from 7-10 days to 9 months

how does corpus luteum maintain hormones during pregnancy

estrogen and progesterone levels maintained

why is chorionic gonadotropin good marker of pregnancy

happens right after fertilization