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Comparative Anatomy

Comparative Anatomy. Evolution of the Postcranial Skeleton. Functional units of the post-cranial skeleton. Visceal skeleton Vertebral column Ribs Sternum. Girdles Paired appendages Unpaired appendages. Evolution of the Postcranial Skeleton. Postcranial Skeleton.

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Comparative Anatomy

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  1. Comparative Anatomy Evolution of the Postcranial Skeleton

  2. Functional units of the post-cranial skeleton. Visceal skeleton Vertebral column Ribs Sternum Girdles Paired appendages Unpaired appendages Evolution of the Postcranial Skeleton.

  3. Postcranial Skeleton • We need to know a little more about bone. • What sorts of forces operate on bony tissue? • Compression • Tension • Shear • Torsion

  4. Forces operating on bone • Examples • Compression……. Graviportal limbs of elephants. • Shear……………..Greater trochanter of the femur. • Torsion…………... Vertebrae & Femur • Tension………….. Sternum

  5. Forces operating on bone • Bone is living tissue, and accommodates whatever forces are applied to it. • As an example, someone who loses a lot of weight quickly will still possess a robust skeleton designed to carry a lot of weight. However, with time the skeleton will reabsorb a considerable amount of tissue and become more gracile.

  6. Forces acting on bone. • We can look at cross-sections of bone and determine exactly what kinds of forces were applied to the bone. • Note - a bone is not solid in cross section. • “force lines” within the bone become ossified for increased strength.

  7. Changes resulting from terrestrialization. • What are some of the problems associated with a terrestrial life style? • Support • Stability • Locomotion • Respiration • Dessication. • Note: some of these same issues are faced by aquatic forms as well.

  8. In an aquatic environment, the water acts as a skeleton. Terrestrial organism often have their mass arranged over only a few points of support.Compare and contrast the articulations of the 2 joints shown here.

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