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Skeletal System I Axial Skeleton

Skeletal System I Axial Skeleton. Why have a skeletal system?. The Skeletal System. Axial skeleton – notochord , vertebral column Appendicular skeleton – girdles, limbs Cranial skeleton – skull. Axial Skeleton.

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Skeletal System I Axial Skeleton

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  1. Skeletal System IAxial Skeleton

  2. Why have a skeletal system?

  3. The Skeletal System • Axial skeleton – notochord, vertebral column • Appendicular skeleton – girdles, limbs • Cranial skeleton – skull

  4. Axial Skeleton • Notochord – stiff (but flexible) rod made up of fibrous connective tissue • Vertebral column – repeating series of cartilaginous or … • Ribs – struts that attach to … • Sternum – muscle origins; rib articulation • Gastralia –ventral ribs in some tetrapods (some lizards, crocodilians)

  5. Bone • = specialized connective tissue with calcium salts deposited in the matrix • Osteoblasts • Osteoclasts • Spongy bone is … • Compact bone appears … Fig. 5.21

  6. Bone Development • Endochondral bone – cartilage “model” replaced by … • Intramembranous bone – formation from mesodermal cells without … • Read pages 182-185 and understand differences between these types

  7. Generalized Vertebral Segment Fig. 8.1

  8. Trends in Vertebral Column Evolution • Changes in the number and structure of individual … • Vertebral components displace notochord as primary mechanical axis • Vertebral components become differentiated along body axis

  9. Vertebral Anatomy • Centra – the … • Intervertebral body (= intervertebral cartilage) • “intervertebral disk” = core of intervertebral body derived from embryonic notochord, or “nucleus pulposus” • Intervertebral ligament – joins rims of…

  10. Types of Centra • Aspidospondyl = ossified elements remain… • Holospondyl = all elements … Fig. 8.3

  11. Articulating Centra Shapes - Both ends concave - Most fish, some salamanders - Both ends flat - Mammals - Posterior end concave - Most salamanders - Anterior end concave - Anurans, modern reptiles - Saddle-like ends - Birds Fig. 8.4

  12. Centra Function Fig. 8.5

  13. Vertebral Innovations • Agnathans – mostly notochord; lamprey with.. • Fishes • Primitive – dorsal and ventral arches, no … • Derived – enlarged elements around … • Tetrapods • One centrum from intercentrum or pleurocentrum See Fig. 8.23 for more info

  14. Why just one prominent centrum?

  15. Apophyses • Processes projecting from centra that articulate • Diapophyses • Dorsal transverse process • Parapophyses • Ventral transverse process • Zygapophyses • Interlocking • Anti-twist & for …

  16. Ribs • = struts that attach to vertebrae (fusion or articulation) • Why have ribs?

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