Final Exam Review - 47.2: Morphogenesis in animals involves...

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47.2: Morphogenesis in animals involves specific changes in cell shape, position and survival DEFINITIONS Morphogensis- The cellular and tissue-based processes by which an animal body takes shape. Gastrulation- In animal development, a series of cell and tissue movements in which the blastula- stage embryo folds inward, producing a three-layered embryo, the gastrula. Organogensis- The process in which organ rudiments develop from the three germ layers after gastrulation. Gastrula- An embryonic stage in animal development encompassing the formation of three layers: ectoderm, mesoderm, and endoderm Germ layer- Ectoderm- The outermost of the three primary germ layers in animal embryos; gives rise to the outer covering and, in some phyla, the nervous system, inner ear, and lens of the eye. Endoderm- The innermost of the three primary germ layers in animal embryos; lines the archenteron and gives rise to the liver, pancreas, lungs, and the lining of the digestive tract in species that have these structures. Mesoderm- GASTRULATION Gastrulation is a dramatic reorganization of the hollow blastula into a two-layered or three layered embryo called: gastrula. Embryonic germ layer : the cell layers produced by gastrulation In late gastrula, ectoderm forms the outer layer and endoderm lines the embryonic digestive compartment or tract. Diploblasts - two germ layers form Triploblasts- three germ layers form Figure 47.8: Major derivatives of the three embryonic germ layers in vertebrates
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**Some organ and many organ systems of the adult derive from more than one germ layer. GASTRULATION IN SEA URCHINS Figure 47.9: Gastrulation in a sea urchin embryo The movement of cells during gastrulation forms an embryo with a primitive digestive tube and three germ layers. Some of the mesodermal mesenchyme cells that migrate inward (step 1) will eventually secrete calcium carbonate and form a simple internal skeleton. Embryos in steps 1-3 are viewed from the front, those in 4 and 5 from the side. 1.) Once the blastula is formed, gastrulation begins with the migration of mesenchyme cells from the vegetable pole into the blastocoel. 2.) The vegetable pole plate invaginates. Mesenchyme cells migrate throughout the blastocel. 3.) Endoderm cells form the archenteron (future digestive tube). New mesenchyme cells at the tip of the tube send out thin extensions (filopodia) toward the blastocel wall (left, LM). 4.) The filopodia then contracts, dragging the archenteron across the blastocel.
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5.) Fusion of the achenteron with the blastocoel wall forms the digestive tube, which now has a mouth and an anus. The gastrula has three germ layers and is covered with cilia, which will function later in feeding and movement. -Gastrulation begins at the vegetable pole.
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Final Exam Review - 47.2: Morphogenesis in animals involves...

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