Histo/Phys: female reproduction tract Flashcards
where are LH receptors?
theca cells
where are FSH cell receptors
granulosa cells
GnRH pulses???
1 GnRH pulse/hr = LH
1 GnRH pulse/3hr = FSH
what happens during follicular phase?
lasts first 14 days, same as proliferative phase
- slight surge in FSH is triggered by declining E and P levels. FSH stimulates cohort of follicles to mature from one ovary. Follicles produce a large amount of estradiol. Levels peak just prior to ovulation and result in a mid-cycle surge of LH through positive feedback loop. This LH surge stimulates ovulation.
What are the stages of ovarian follicle maturation?
- primary follicle with primary oocyte (46 cs, diploid 4n)
- primary unilaminar follcles: 1 oocyte rapidly grows
- multilaminar primary follcicles “granulosa cells”
4/5. secondary “antral follicle” - graafian mature follicle
what does primordial follcle contain?
primary oocyte
contains 46 css (diploid, 4N DNA) arrested in prophase of 1st meiotic division (and remain so for 12-50 yrs)
squamous follicular cells surround primary oocyte joined by desmosomes separated from stroma by BM
what is contained in primary unilaminar follcicle?
oocyte rapidly grows
follicular cells become cuboidal
zona pellucida begins to form, but not visible
zona pellucida - glycoprotein coat separates oocyte from follicular cells
multilaminar primary follicles?
follicular “granulosa cells” become multilayered these cells pass small precursor molecules to nurture oocyte
zona pellucida continues to develop
theca interna begins to be visible - differentiates from stroma around follicle
secondary antral follcicle?
antrum appears: hollow space
granulosa cells (follicular cells) continue to proliferate
synthesize & secrete estrogens (estradiol, estrone)
theca interna matures, theca externa begins to develop
Secondary follcile theca cells?
Theca interna developes in secondary follcile and cells become cuboidal. They develop features of steroid producing cell (synthesize testosterone and androstenedione under influence of LH, which is converted to estradiol and estrone via granulosa cells)
- separated from granulosa cells by well developed BM
- Theca externa begins to develop as CT arrayed around theca interna.
components of graafian mature follicle?
- antrum is enlarged and filled with liquor folliculi (contains steroid hormones, GAG’s and inhibin)
- zona pellucida is well developed
- cumulus oophorus = hillock of cells supporting the oocyte
- corona radiata = granulosa cells that surround the oocyte, these are retained with oocyte at ovulation and must be penetrated by sperm. They are reqd to transport ova in oviduct.
what causes ovulation?
high circulating levels of estrogen produced by granulosa cells results in positive feedback on FSH and LH. The LH surge leads to ovulation and the stigma ruptures elaborating oocyte (involves proteases such as plasmin)
- this results in a release of bloood and blood fills remaining follciular antrum, called corpora hemorrhagium
what happens at ovulation?
- primary oocyte completes 1st meiotic division to produce secondary oocyte (23 2n) and polar body
- after ovulation the oocyte is picked up by finbriae and enters infundibulum (oocyte is transported to uterus via peristalsis primarily and also by ciliary action)
- Oocyte enters 2nd meiotic division but is suspended in metaphase II until fertilization
- if oocyte is fertilized, it will finish second meitoic division and will produce an ovum (haploid 23, 1n)
ovulation vs. atresia?
ovulation usually produces single fertilizable oocyte, but a cohort of follicles form under FSH influence. 1 dominant follicle emerges about 1 week before ovulation
in follicular atresia: oocyte dies and antrum collapses. granulosa cells stop dividing, detach from basal lamina. during atresia some theca interna cells persist, make up “insterstitial glands” which secrete androgens through out life.
neonatal ovary?
primordial germ cells (oogonia) proliferate in genital ridges and continue to develop until they arrest in prophase I of meiosis (reached at 7th month of fetal life)
- fetus/neonatal ovaries show features of maturing and menarche
menarche?
establsihment of menstrual function
- at puberty pituitary gonadotropins increase leading to cyclic maturation of primordial follicles.
- during pre-pubertal period primordial follcilces being to mature though most are fated for atresia
400,000 follcicles at birth, only 150,000 follicles available at menarche
menopause?
cessation of menstrual cycle
- number of follicles becomes vanishingly small
- absence of follcicles
- theca interna cells remain producing androgens
What happens during luteal phase?
Corpus luteum formation occurs after ovulation and serves as the source of progesterone (peaks in the mid-luteal phase). Luteal hormonal output is dependent on LH and both FSH and LH levels decline to basal levels in the luteal phase (in part due to prodution of inhibin A). The corpus luteum will die in 14 days unless rescued by HCG from the implanted embryo.
What happens to corpus luteum during pregnancy?
- It persists and continues to produce high levels of estrogen and progesterone.
- it expands during pregnancy b/c of triggering from LH, but later LH starts to decline. Thus CL is maintained for 6 mos. by the hormone hCG.
during later stages of pregnancy CL secretes polypeptide hormone relaxin which increases pliability of pelvic CT and faciliates parturition.
What is corpus albicans
scar left after involution of CL. It will partially or completely involute with time.