Fertilization + Cleavage Flashcards
How/where does Fertilization happen?
Sperm and Oocyte join forming a Zygote in the ampullary region of Fallopian tube
What excites sperms again in isthmus?
Chemo attractants produced by cumulus cells, increasing motility
What is capacitation?
Occurs in fallopian tube, glycoprotein coat and plasma proteins removed from acrosome of spermaozoa, allowing for acrosome reaction
Acrosome reaction
Induced by Zona pellucida proteins, releasing acrosomal enzymes (esterase, collagenase, acrosin, neuraminidase)
FIRST barrier sperm encounter in fertilization
Granulosa cells (Corona radiata), embedded in loose ECM, only capacitated sperm can pass through
SECOND barrier sperm encounter in fertilization
Zona Pellucida, sperm-specific glycoprotein coat, prevents immature implantation
What receptor is in Zona Pellucida?
ZP3 receptor allows sperm binding
What happens to oocyte when sperm touches it?
Cortical reaction, alters zona pellucida preventing more spermatocytes in
What mediates adhesion of sperm to oocyte?
Integrins on oocyte, Disintegrins on sperm
What happens after sperm and egg membranes fuse?
Second meiotic division of oocyte continues, second polar body formed + definite oocyte, metabolic act. of egg, male and female pronucleus with chromosomes (Haploid)
Results of fertilization
Diploid number of chromosomes, Determination of sex, Cleavage initiation
Polyspermy blocks types
Slow and Fast
Fast polyspermy block
Quick calcium influx, modifying electric potential of oocyte (+ to -) preventing other sperm to fuse
Slow polyspermy block
Lysozomes from cortical granules released btw oocyte and zona pellucida, Alter ZP3 making ZP impermeable (Zona + Cortical reactions)
What is cleavage?
Series of mitotic divisions after zygote 2-cell stage
