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Axial Skeleton - Vertebrae

Axial Skeleton - Vertebrae. Locomotion Protects spinal cord Suspends trunk. Vertebrae. Centrum Body of vertebra Surrounds or replaces notochord. Centrum shape. Amphicelous (most fish, tailed amphibians) Opisthocelous (terrestrial salamanders, gar) Acelous (mammals)

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Axial Skeleton - Vertebrae

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  1. Axial Skeleton - Vertebrae • Locomotion • Protects spinal cord • Suspends trunk

  2. Vertebrae • Centrum • Body of vertebra • Surrounds or replaces notochord

  3. Centrum shape • Amphicelous (most fish, tailed amphibians) • Opisthocelous (terrestrial salamanders, gar) • Acelous (mammals) • Procelous (reptiles, frogs)

  4. Vertebrae • Vertebral arch • Neural arch • Neural spine = spinous process • Neural canal = vertebral canal

  5. Vertebrae • Hemal arch • Chevron bone in amniotes • Ventral archway for caudal blood vessels • Hemal spine

  6. Vertebrae • Transverse process • Diapophysis

  7. Vertebrae • Zygaphophyses • Tetrapod feature • Prezygapophyses – cranial • Postzygapophyses - caudal

  8. Development of vertebrae • Ancient • Sclerotomes around notochord • Intersegmental from the somites • Cartilage replacement of notochord • Bone replacement of notochord

  9. Vertebrae in advanced fish • Centrum replaces notochord • Diplospondyly in tail

  10. Vertebrae in fish • Regional differentiation • Dorsal = Trunk • Caudal = tail

  11. Vertebrae - fish • Craniovertebral joint • No movement

  12. Vertebrae - Amphibians • Terrestrial life • Spine must support body • Resists bending but provides mobility

  13. Phylogeny of tetrapod vertebrae • Tetrapod centrum is the descendant of the Pleurocentrum, not the intercentrum

  14. Vertebrae - amphibians • Zygapophyses

  15. Vertebrae - amphibians • Regional differentiation • Cervical – usually one • Trunk = dorsal – ribs present • Sacral – one • Caudal – no zygapophyses • Urostyle – fused post-sacral vertebrae in anurans

  16. Skeletal support Sacral vert. Cervical vert. Trunk vert. with ribs Caudal vert.

  17. Vertebrae - amphibians • Craniovertebral joint • 1-2 occipital condyles

  18. Vertebrae - Reptiles • Centrum replaces notochord • Procoelous centrum • Pleurocentrum is phylogenetic ancestral centrum

  19. Vertebrae - Reptiles • Zygapophyses • Not in tail

  20. Vertebrae - reptiles • Cervical – 8 including atlas and axis • Dorsals = Trunk (thoracic and lumbar) • Sacral – 2 for stronger support • Caudal • Chevron bone = hemal arch • Autonomy

  21. Vertebrae - reptiles • Craniovertebral joint • Ball & socket type of joint • Single occipital condyle

  22. Vertebrae - reptile • Atlas = C1 • Axis = C2 • Odontoid process for rotation • Proatlas in crocodiles anterior to atlas

  23. Vertebrae - Birds • Centrum is heterocoelous

  24. Vertebrae - birds • Numerous cervical vertebrae • Single occipital condyle • Trunk = Thoracic vertebrae (tend to fuse) • Synsacrum • Last thoracic, all lumbar, 2 sacral, some caudal • Caudal vertebrae • Pygostyle supports tail feathers

  25. Vertebrae - Mammals • Centrum is acelous • 7 cervical • Thoracics vary • Lumbars vary • Sacrum 3-5 • Caudal • Chevron bone • Coccyx

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