Embryology2

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Embryology2

  1. 1. HUMANEMBRYOLOGY
  2. 2. PERIODS OF EMBRYOGENESIS1. FERTILIZATION AND ZYGOTE FORMATION2. CLEAVAGE3. GASTRULATION.4. HISTO- AND ORGANOGENESIS
  3. 3. CHARACTERISTICS OF GAMETESOOCYTE SPERMATOZOA
  4. 4. CHARACTERISTICS OF GAMETES
  5. 5. FERTILIZATION
  6. 6. FERTILIZATION
  7. 7. FERTILIZATION
  8. 8. CLEAVAGE
  9. 9. CLEAVAGE
  10. 10. IMPLANTATION
  11. 11. EARLY GASTRULATION
  12. 12. EXTRAEMBRYONIC ORGANS FORMATION
  13. 13. LATE GASTRULATION
  14. 14. DIFFERENTATION OF GERM LAYERS
  15. 15. 22-23 days pf Human
  16. 16. 23-26 days pf Human
  17. 17. Formation of the Neural Tube• Secondary Neurulation 1. Occurs beyond the caudal neuropore 2. lumbar and tail region 3. Exclusive mechanism for fish 4. Starts with formation of medullary cord 5. Cavitation of cord to form hollow tube
  18. 18. Differentiation of Neural Tube• Major morphological changes: differentiation of brain vesicles and spinal cord• Differentiation of neural tube cells• Development of peripheral nervous system
  19. 19. Neural Crest Cells• Migration: – Epithelial to mesenchyme transition – Migrational pathways are established by juxtacrine signals: • Fibronection, laminin in ECM + integrins • Ephrin proteins: Restrict movement • Contact inhibition • Use of existing structures – Migration ceases when these signals are reversed
  20. 20. Neural Crest Cells• Differentiation: – Largely based on location along neural tube and their migration route:
  21. 21. Neural Crest Cells• Differentiation: – Migration routes along trunk: – Ventral pathway: cells move through anterior portion of somite toward ventral side of embryo • Cells become: sensory neurons, sympathetic ganglia, medulla of adrenal gland – Dorsolateral pathway: cells move between epidermis and somite • Cells become: melanocytes• Basic organization of the PNS is established by the migratory pathways of the neural crest cells

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