01:119:116 Lecture Notes - Lecture 17: Archenteron, Hypoblast, Polarity In Embryogenesis
22 Apr 2016
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Document Summary
After cleavage: normal cell cycle resumes, cell division slows, morphogenesis: process by which animal body takes shape; occurs during gastrulation and organogenesis. Gastrulation: morphological process by which hollow blastula becomes layered embryo (gastrula: embryonic germ layers. Mesoderm: forms between ecto and endo: diploblasts (ecto & endo) vs triploblasts (ecto, endo, meso, gastrulation in 4 species. Blastopore: open end of archenteron, becomes anus. Frogs (vertebrates: a. mesenchyme cells at vegetal pole migrate into blastocoel secrete. Bilateral symmetry: cell movement begins on dorsal (back) side of blastula; opposite of where sperm entered. Involution continues - archenteron grows and displaces blastocoel (eventually disappears); yolk plug surrounds blastopore: ectoderm spreads from animal to vegetal blastopore shrinks, late gastrulation: ecto and endoderm formed with meso in between; yolk plug blocks archenteron. Epiblast: upper layer all cell will form embryo. Hypoblast: lower layer don"t contribute to embryo. Sequence of events: epiblast cells migrate towards midline detach move towards yolk.
