Embryology

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Embryology
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Fertilization

• Enzymes in acrosome (tip of sperm) dissolve jelly
  layer around egg
• Sperm membrane fuses with egg membrane, nucleus
  enters egg
• Other sperm are prevented from entering egg
• Egg and sperm nuclei fuse

3
Cleavage

• Cleavage is a series of mitotic divisions
  whereby the egg cytoplasm is cleaved into smaller
  cells

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Stages of Cleavage

• Morula solid ball of cells which secrete fluid
  to the inside to make a hollow ball of cells, the
  blastula
• Blastula hollow ball of cells, with fluid
  filled cavity called the blastocoel

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Gastrulation

• It is not birth, marriage or death,but
  gastrulation, which is truly themost important
  time in your life.        Lewis Wolpert (1986)
• Cells move and invaginate to rearrange the cells
  of the blastula
• Establishes 3 germ layers that differentiate
  into specific tissues in the organism

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Three Primary Germ Layers

• Ectoderm outermost layer, becomes the skin,
  CNS, sense organs
• Mesoderm middle layer, becomes skeleton,
  muscles, blood vessels, heart, gonads
• Endoderm inner layer, becomes digestive tract,
  lungs, glands

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Neurulation

• In vertebrates, a dorsal nerve cord form from the
  ectoderm
• It folds over to form a tube
• The larger part becomes the brain

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Human Embryology

• Hyperlink below will go to a website which goes
  through all the stages of human embryonic
  development