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Ontogeny recapitulates phylogeny

Ontogeny recapitulates phylogeny. EVOLUTION & DEVELOPMENT. 3 examples of this principle head head vasculature u-g system. The vertebrate head Brachiomeric organisation. Skate embryo. Brachiomeres formed by migrating neural crest and filling up indentations in the ectoderm.

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Ontogeny recapitulates phylogeny

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  1. Ontogeny recapitulates phylogeny EVOLUTION & DEVELOPMENT • 3 examples of this principle • head • head vasculature • u-g system

  2. The vertebrate head Brachiomeric organisation

  3. Skate embryo

  4. Brachiomeres formed by migrating neural crest and filling up indentations in the ectoderm

  5. Components of a brachiomere - nerve, muscle, cartilage, blood vessel

  6. Nerve comes from nearby CNS/neural crest Cartilage differentiates from neural crest Blood vessel from aorta Muscle from somites

  7. What about us?

  8. Trigeminal (V) Facial (VII) Glossopharylgeal (IX) Vagus (X)

  9. Orofacial clefting

  10. Heart and circulatory system

  11. Heart fate map

  12. ANT truncus arteriosus bulbus cordis primitive ventricle atrioventricular canal primitive atrium sinus venosus Now starts looping POST

  13. Loops to right 25 days 24 days

  14. Differences between the chambers now clearly apparent

  15. Now, having fused 2 tubes together, they have to split into 2 again. Atrioventricular canal – endocardial cushions

  16. Aortic arches - 6 in us too, only briefly

  17. Modification of the 6 arch ground plan

  18. U-G system

  19. Yolk sac Allantois bladder

  20. Nephric system Gonads Genital ducts

  21. Segmental structures called nephrotomes form from anterior end in sequence. Nephrotome form a simple duct in each segment and an archinephric duct which joins each nephrotome up. Branch of dorsal aorta buds out into each nephrotome. Simple kidney which drains in to coelom = PRONEPHROS (HOLONEPHROS) Seen in ANAMNIOTES embryos and larvae and hagfish

  22. METANEPHROS is functional kidney in amniotes

  23. Each of these stages can be seen in human embryos – pronephros, mesonephros becomes part of male genital duct system, metanephros – functional kidney

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