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HUMAN EMBRYOLOGY

HUMAN EMBRYOLOGY. After fertilization of the egg, let the division begin!. Cleavage follows fertilization. A zygote is formed when the egg is fertilized. Cleavage is a series of rapid mitotic divisions (without cell growth).

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HUMAN EMBRYOLOGY

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  1. HUMAN EMBRYOLOGY

  2. After fertilization of the egg, let the division begin!

  3. Cleavage follows fertilization • A zygote is formed when the egg is fertilized. • Cleavage is a series of rapid mitotic divisions (without cell growth). • The two-celled zygote divides repeatedly until a ball of 32 cells is formed. • This is the morula - 32 cells.

  4. Continued divisions make the hollow blastula. • These few cells are pluripotent (have the potential to become ANY of the 220 types of cells in the human body). • These are embryonic stem cells.

  5. Gastrulation • At the end of the cleavage stage, cells making up the blastula move about in a very purposeful and orchestrated manner with the help of surface proteins to recognize each other. • The gastrula, which consists of 3 “germ layers” is formed. • Layers - Endoderm, Mesoderm, & Ectoderm

  6. Germ Layers • Endoderm – Inner Layer; becomes the inner lining of most systems: digestive, respiratory, etc. • Mesoderm – Middle Layer; becomes muscles, bones, some skin tissue, connective tissues, the reproductive and urinary systems and other internal organs. • Ectoderm – Outer Layer; becomes the nervous system, tooth enamel and the epidermis. It also forms the lining of mouth, anus, nostrils, sweat glands, hair and nails.

  7. Gastrulation

  8. Human Development • The gestation period lasts 266 days from fertilization to birth. • Organogenesis (development of the organs and organ systems) begins with the nervous system.

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