Lecture 7 Female Reproductive Physiology Flashcards
Outline the stages of an ovarian follicle.
Primary follicle - Secondary follicle - Mature follicle - Ovulated oocyte, Corpus Luteum
How long does the follicular and luteal phase occur?
14 days each
What occurs during early to mid-follicular phase?
Low oestrogen exert negative feedback on GnRH, LH, FSH.
Oestrogen has +ve feeback on granulosa cells to produce more oestrogen.
Granulosa cells also produces AMH which prevents recruitment of additional follicles
What occurs during late follicular phase?
Oestrogen has increased to high oestrogen levels, which has positive feedback on GnRH, causing LH and FSH secretion. FSH acts on granulosa cells to produce oestrogen and inhibin. Inhibin has negative feedback on FSH, so FSH surge remains low. LH acts on thecal cells to produce androgens.
What occurs during early to mid luteal phase?
After ovulation, corpus luteum forms. Luteal cells produce high levels of oestrogen, progesterone, and inhibin. These factors have negative effect on GnRH, LH and FSH release.
What occurs during late luteal phase?
Corpus luteum spontaneously dies after 12 days if pregnancy does not occur. Oestrogen and progesterone levels drop, cause tonic secretion of GnRH and hence FSH and LH to occur again.
What are the observations in the uterine epithelium during pre-receptive phase?
Function is to impair attachment: so long apical microvilli, thick glycocalyx, -ve charge to repel blastocyst, tight junctions and focal adhesions.
What are the transformations seen in the uterine epithelium during the receptive phase?
Function is to allow close apposition of blastocyst to uterine wall, facilitating attachment:
Apical protrusions absorb uterine fluid, this decreases uterine cavity
Microvilli shorten
Glycocalyx thins
Loss of -ve charge
Tight junctions extend down
Focal adhesions lost completely
Integrins migrate from basal lamina to apical surface
How is receptivity regulated by hormones?
Mostly by oestrogen and progesterone. Increased receptor expression after ovulation.
Oestrogen travels through blood vessels, regulates production of glycocalyx
How are focal adhesions and tight junctions assembled during non-receptive phase?
Focal adhesions are at the basal side of the cell. Between the actin cytoskeleton of a cell, via integrin transmembrane proteins, to extracellular domain. Allows signal transduction between cell and ECM.
Tight junctions are made up of zona-occludens 1 on lateral side of cell, near apical. Provides a barrier to movement of substances across epithelium
How do focal adhesions and tight junctions change during uterine receptivity?
Focal adhesions diassemble completely.
Integrins move to apical cell, expressed outside of UEC to allow attachment with integrins of blastocyst.
Tight junctions ZO-1 move apart to allow substances to move across, so decrease fluid in uterine cavity
How is meiotic arrest maintained in an oocyte?
Gap junctional communication between the oocyte and granulosa cells. LH causes natriuretic peptide receptor 2 ligand from mural (outside) granulosa cells bind to its receptor on cumulus (inside) granulosa cells. Cause production of cGMP which inhibits activity of PDE3A, inhibiting breakdown of cAMP. cAMP is responsible for maintaining arrest.
Outline the modes of signalling between oocyte and granulosa cells.
Paracrine signalling from cumulus to oocyte and in other direction. And gap-junctional signalling.
What prevents apoptosis of cumulus cells? Effect of removing the oocyte? Why are outer layers more apoptotic?
Oocyte-secreted factors, also enhances oocyte developmental competence (chance of becoming healthy embryo). Increase in apoptosis of inner cumulus cells. More apoptotic in outer layer because paracrine/gap junction signalling only occurs over short distances.
What is the maternal age effect?
Older women have a higher incidence of abnormalities because oocytes are held in meiosis 1 for longer
