Cleavage to Hatching Flashcards
(20 cards)
What is cleavage?
Rapid mitotic divisions without growth that transform the zygote into blastomeres
What type of cleavage occurs in mammals?
Holoblastic, rational, asynchronous, and slow
What is the purpose of cleavage?
Increased nuclear-to-cytoplasmic ratio and prepares for differentiation
At what stage does compaction occur?
8-cell stage
What protein mediates compaction?
E-cadherin
What does compaction establish in cells?
Apical-basal polarity
What forms from inner cells after compaction?
Inner cell mass (ICM)
What forms from outer cells after compaction?
Trophectoderm (TE)
Which transcription factor specifies trophectoderm?
Cdx2
Which transcription factors maintain pluripotency?
Oct4, Sox2, Nanog
What is cavitation?
Formation of a fluid-filled cavity (blastocoel) within the morula
What drives cavitation?
Na+/K+ pumps and aquaporins in trophectoderm
What is a blastocyst?
A structure with an ICM, trophectoderm, and blastocoel
What is the fate of the ICM?
Forms the embryo proper
What is the fate of the trophectoderm?
Forms the placenta
What is hatching?
The blastocyst emerging from the zone pellucida
Why is hatching important?
It allows implantation into the uterus
What triggers hatching?
Proteolytic enzymes and blastocyst expansion
What are the stages in order?
Zygote - 2-cell - 4-cell - 8-cell - morula - blastocyst - hatching
Why is zona pellucida important in pre-hatching?
Prevents ectopic implantation and polyspermy
