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Embryology and Body Cavities

Embryology and Body Cavities. Lecture 3. Tissue Development. Zygote (fertilized egg) undergoes rapid cell divisions called cleavage Forms a hollow ball of cells called the blastula. Blastula. Tissue Development Continued. Archenteron.

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Embryology and Body Cavities

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  1. Embryology and Body Cavities Lecture 3

  2. Tissue Development • Zygote (fertilized egg) undergoes rapid cell divisions called cleavage • Forms a hollow ball of cells called the blastula Blastula

  3. Tissue Development Continued Archenteron • The blastula INVAGINATES (folds inward at one point) • Called Gastrulation • The opening is called the blastopore • The center is the primitive gut or Archenteron Gastrula blastopore

  4. Embryonic Development

  5. Tissue Development • Protostomes-mouth forms from blastopore • Mollusks, Annelids, Arthropods • Deuterostomes- anus forms from blastopore • Echinodermata, Chordata

  6. Germ Layers • Germ layers forms tissues, organs, and systems • 3 Types of Germ Layers • Ectoderm • Mesoderm • Endoderm

  7. 3 Germ Layers • Ectoderm- outer most layer • Gives rise to: • Epidermis (skin) • Nervous system

  8. 2. Mesoderm-middle layer • Gives rise to: • Muscles • Skeleton • Blood System

  9. Endoderm- inner most layer • Gives rise to: • Digestive Organs • Lungs • Bladder

  10. Three Types of Organisms • Multicellular-have no tissue layers at all • Sponges • Diploblastic-have only Ectoderm and Endoderm • Cnidarians (jellyfish, sea anemones) • Triploblastic-have all three layers • Mollusks, arthropods, echinoderms, chordates, etc.

  11. Benefit of Having a Body Cavity? • Provides room for organ development • Provides more surface area for gas exchange and nutrient absorption • Provides for storage area

  12. Benefits Cont’d • Can act as a hydrostatic skeleton • Allows for waste removal • Allows for increased body size

  13. Triploblastic Organisms • Have three Coelom (body cavity) patterns • Acoelomate • Pseudocoelomate • Coelomate

  14. Acoelomates • Have a solid mass of Mesoderm cells between the Endoderm and Ectoderm layers • Ex. Flatworms

  15. Pseudocoelomates • The cavity is not entirely lined by mesoderm • Ex. Nematode (worm)

  16. Coelomates • The body cavity is completely surrounded by mesoderm. • Ex. Human

  17. Triploblastic Body Plans Acoelomate Pseudocoelomate Coelomate

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