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Transue-Lecture2 - I Development a Stages of...

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I. Development a. Stages of development (humans) i. Cleavage ii. Blastulation iii. Gastrulation iv. Organogenesis 1. neurulation 2. other systems b. control of development i. what controls? 1. cytoplasmic substances 2. induction ii. evidence/cloning Fig 49-14, page 973 Morula about 32 blastomeres nearing uterus 3 days old Blastulation Change in structure but not in size o Changing internal organization o Going from solid mass to hollow structure o Cells moving outwards Blastula/blastocyst In humans: From outside looks like sea urchin (about 7 days old) Outer layer is called trophoblast gives rise to placenta Inner cell mass becomes embryo Space is blastoseal Human blastocyst: Outer layer endometridum Separating layer tropoblast Little dark spot embryo P 974 Twins: Identical (monozygotic): Totipotency -- can give rise to anything in the placenta Pluripotency – starts to narrow down can only adult organs
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Conjoined twins:
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