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chap 16 notes

chap 16 notes - cells from animal pole move down over...

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Chapter 16 KEY CONCEPTS Learning Objective 7 * Identify the significance of gastrulation in the developmental process, and compare gastrulation in the echinoderm (or in amphioxus), the amphibian, and the bird Germ Layers * During gastrulation, the blastula becomes a three-layered embryo (gastrula) and the basic body plan is laid down as 3 germ layers 1. outer ectoderm 2. middle mesoderm 3. inner endoderm * New cell-to-cell relationships are formed and the internal architecture of cells change Gastrulation 1 * In sea star and amphioxus * Vegetal pole cells from blastula wall flatten and then invaginate * eventually meet opposite wall, obliterating the blastocoel and forming archenteron * Forerunner of digestive tube * Newly formed cavity of the developing gut in some groups * Blastopore opening of archenteron, to the exterior * Future anus in deuterostomes Gastrulation 2 * In the amphibian (frog) * invagination at vegetal pole obstructed by large, yolk-laden cells
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Unformatted text preview: * cells from animal pole move down over yolk-rich cells and invaginate, forming dorsal lip of the blastopore * yolk-filled cells fill the space enclosed by the lips of the blastopore, forming yolk plug * Blastocoel disintegrates, archenteron forms Gastrulation in Frogs 3 (Fig 50-9) Gastrulation in Birds 4 (Fig 50-10) Learning Objective 8 * Define organogenesis * Summarize the fate of each of the germ layers Organogenesis 1 * Gastrulation leads to organogenesis: * The process of organ formation * Ectoderm becomes * nervous system * sense organs * outer layer of skin (epidermis) Organogenesis 2 * Mesoderm becomes * notochord * skeleton * muscles * circulatory system * excretory and reproductive * inner layer of skin (dermis) * Endoderm becomes lining of the digestive tube * Including liver, pancreas and lungs...
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