01:119:101 Lecture Notes - Lecture 12: Primitive Streak, Inner Cell Mass, Epiblast
12 Jul 2015
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This now results in double walled, cup, shaped structure. Inner wall, lines archenteron, newly formed cavity of developing gut will eventually become the digestive tract. Cells constantly migrate from epiblast inward to primitive groove, then sink down and move laterally: henson"s node thickened area at anterior end of primitive streak these cells are eventually going to form the nototchord. Mammalian development: fertilization - in oviduct, cleavage in oviduct, embryo no obvious polarity; cleavage divisions therefore oriented randomly until the formation of the blastula, no yolk, division is holoblastic. These cells will secrete enzymes, and the enzymes will allow the embryo to penetrate the endometrium: trophoblasts are also going to thicken and extend finger-like projections into the endometrium this is implantation. Day 12 chapter 51: placenta forms from proliferated trophoblast and endometrium. Provides o2 and nutrients remove wastes excreted by mother. Also serves as endocrine organ secretes estrogen, progesterone.
