DASC20010 Lecture Notes - Lecture 2: Zona Pellucida, Morula, Blastocoel
23 Jul 2018
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Cell movement (migrate to specific points in the embryo by use of a concentration gradient towards the concentrated end) During post-natal development cell size can increase as well as in number. Produces smaller cells called blastomeres (each time split, each cell is half the size) Pattern of cleavage depends on size of yolk: avian (massive volume of yolk, cleavage is partial- meroblastic, placental mammals (minimal yolk, cleavage is total- holoblastic) Cleavage results in a solid cluster of cells- morula. Blastomeres lose spherical shape and become tightly apposed- campaction. Secretions from blastomeres accumulate in morula- blastocoel (embryo called blastocyst) Eruption/hatching- if this does(cid:374)"t happe(cid:374) preg(cid:374)a(cid:374)(cid:272)y does(cid:374)"t happe(cid:374) Marked increase in size and shape: blastocoel enlargement, species specific. Hatch forces: growth and fluid accumulation, enzyme production by trophoblast. In rodents and horses the zona degenerates (queen= cat) Inner cell mass- the little white stuff on top of the yolk.
