Biology 3338A Lecture Notes - Bone Morphogenetic Protein 7, Notochord, Germinal Disc
3 Apr 2014
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Have amniotic sac, form extra embryonic tissues like we do. Don"t attach to uterus, don"t really have placenta in same way. Have huge yolk, embryo forms in sac on top of yolk, uses yolk to feed off of. Extra embryonic tissues to latch onto yolk and use it, attach to nutrient source. Initially: one fertinlized 2n nucleus in yolk, nucleus starts to form membranes, end up with cellular yolk-free group of cells called blastodisc sitting on top of yolk. Initially 1 cell layer thick, doesn"t contain yolk, forming cells on top of yolk. Cleavages not going through yolk, form clear area called blastodisc. End up with fertilized 2n nucleus, will divide and start to form cells on top, don"t cleave into yolk, are free of yolk basically. Cleavages on top of yolk, initially 1 cell layer thick (blastodisc), eventually thicker. Get layer of cells sitting on top of yolk. Cells then begin to secrete albumin beneath them.
