Hellkatz: Female Reproductive Cycle Flashcards
What is the purpose of mitosis in oogenesis?
Create a larger pool of primary oocytes (46, 2N)
What is the purpose of Meiosis in oogenesis?
ONE of the primary oocytes develops into a secondary oocyte (23, 2N) and is ovulated per month (ready for fertilization)
When is the second meitotic division completed?
after fertilization
What stimulates meiosis 1 and the development of primary follicles into secondary follicles?
LH surge
What is recruitment?
During the final stage of development 6-8 follicles are recruited to get bigger, the largest wins and is ovulated while the rest undergo atresia.
What hormones are dominant in the follicular phase?
estrogen (increased)
progesterone (decreased)
What hormones are dominant in the luteal phase?
Increased progesterone
What happens to the graafian follicle once ovulation occurs?
Graafian follicle (granulosa cells and theca cells) undergoes transformation to luteal cells and produces PROGESTERONE (key indicator of luteal phase)
*if pregnancy occurs, progesterone production increases until the placenta takes over
What happens to the corpus luteum if pregnancy doesn’t occur?
CL regresses and the cycle repeats
What is folliculogenesis?
The growth of primordial follicles to pre-ovulatory follicles. Follicles in develop in cohort but only one is ovulated.
What is a primordial follicle?
primary oocytes surrounded by follicular cells (granulosa and theca cells)
What are all the oogonia at birth?
primary oocytes (all you got for a life time!)
What happens to primordial follicles during a lifetime?
Most progress to primary follicles until they’re all exhausted….that’s menopause.
What is cyclic recruitment?
antral follicles that are rescued by FSH
What is the Graafian follicle?
The dominant follicle is the largest and produces the most hormones and develops LH receptors. It becomes the ovulatory follicle and ruptures in response to a surge in LH.
What promotes follicle development and LHR synthesis?
FSH
What promotes estrogen synthesis?
FSH/LH
Describe the normal state of the HPOA.
Hourly GnRH pulses> FSH/LH basal secretion> estrogen> NFB on pituitary> reduces FSH/LH secretion
What happens to estrogen close to ovulation?
HIGH estrogen state that feeds bake positively
Antral follicles produce HIGH levels of estrogen>
induces rapid GnRH pulses>
increased FSH/LH
What does inhibin do?
Inhibits FSH but not LH>
leading to the LH surge
Where is GnRH produced?
Arcuate nucleus of the Hypothalamus
10 AA polypeptide
What type of membrane protein does GnRH signal through?
Targets gonadotrophs>
Membrane G protein coupled protein Gq>
activates PLC>
DAG, IP3
Why is the manner that GnRH is secreted important?
Pulsatile (can use it as a fertility treatment)
What are the gonadotropins of the AP?
FSH (folliclular growth, estradiol secretion)
LH (critical for inducing ovulation, ovulation is required for formation of CL)
What gonadotropin is targeted for contraception?
LH
What gonadotropin is formed in the placenta?
hCG
What maintains the corpus luteum in the first trimester keeping progesterone and estrogen levels high? What happens later in pregnancy?
hCG
Placenta takes over steroidogenesis/pregnancy maintenance
What distinguishes gonadotropins?
They’re all glycoprotein hormones with identical alpha subunits but different beta subunits
What happens to serum concentrations of gonadotropins with removal of the ovaries or menopause?
serum concentrations INCREASE
What type of receptors respond to Gonadotropins?
Gs protein copuled
What does LHGCR/LHR bind?
both LH and hCG
What does the ovary require for steroidogenesis?
both LH and FSH
What stimulates thecal cells around the follicles to produce progesterone and androgens?
LH
What happens to androgens produced in thecal cells?
Diffuse across the basement membrane to the granulosa cell layer where FSH stimulates aromatize to convert them to estrogens (mainly estradiol 17B.
What estrogen receptor mediates the HPO axis response to estrogen?
ER alpha
Describe the ovarian cycle.
- Small pulses of LH/FSH stimulate folliclular growth and secretion of ovarian steroid hormones
- High estrogen levels increase GnRH pulses>
LH surge> Ovulation - Ovulation induces leutinization> formation of hte corpus luteum> produces high levels of progesterone and estrogen
- If fertilization doesn’t occur> spontaneous luetolysis of corpus luteum> decrease in progesterone/estrogen levels
What do hormonal contraceptives do?
Suppress LH surge
Provokes uterine growth, predominant steroid PRIOR to ovulation
Estrogens
Maintain metabolic activity in the uterus, predominant steroid AFTER ovulation
Progestins
Thickens/proliferation of endometrium
Development of glands from cuboidal to pseudostratified
Stroma/vessel growth
Tenfold increase in uterine lining
Estrogens
Halts further growth of endometrium
Secretions from glands
Progesterone
What leads to the maternal RECOGNITION of pregnancy?
chorion production of hCG that promotes the maintenance of the corpus luteum> progesterone and estradiol
What leads to MAINTENANCE of pregnancy?
placenta production of hormones (hPL, inhibin, estrogen, PROGESTERONE)
Blastocyst in uterus
Days 4-5
Implantation leading to rise of hCG and maintenance of corpus luteum
Days 5-9
How long does hCG maintain the corpus luteum?
3-4 mos until placenta becomes primary source of PROGESTERONE which is required for preg maintenance
What is used as a pregnancy indicator?
Urinary hCG (esp after 1 week)
When is the greatest likelihood of miscarriage?
At the end of the first trimester when transition occurs and uterine dependence shifts from ovarian to placental steroids
What hormonal shift occurs with parturition?
Shift from P>E dominance to E> P dominance
What happens during pregnancy when P>E?
Progesterone>
- hyperpolarization of myometrial cells preventing contraction
- inhibits oxytocin
- Inhibits ER synthesis
- Promotes storage of PG syth enzymes
What happens during delivery when E>P?
- Increase OT receptors
- Uterine contractility
- Uterine ripening
- Increased PG release form placenta>myometrial contracitons
- Oxytocin release form PP> stronger myometrial contractions
What’s responsible for mild Braxton Hicks contractions during preganncy?
PG (Produced in placental unit)
What induces smooth muscle contraction and is positively autoregulated?
Oxytocin
What is mammogenesis?
Development of epithelial duct tree (estrogen, glucocorticoids, GH dependent)
What stimulates lobular alveolar growth?
progesterone
prolactin
What happens in lactognesis I?
lobular alveolar growth in mid to late pregnancy
What happens in lactogenesis II?
post partum onset of copious milk secretion that comes with the fall of progesterone after delivery (dependent on prolactin)
What maintains lactation?
Prolactin/removal of milk
What leads to milk ejection?
oxytocin
What leads to involution?
lack of prolactin
