BISC 316 Lecture Notes - Lecture 21: Shoulder Girdle, Stratum Corneum, Dermal Bone

• School: Simon Fraser University
• Department: Biological Sciences
• Course: BISC 316
• Professor: Joan Sharp

Document Summary

Changes to skull and cervical vertebrae of tetrapods, how they altered/improved feeding and head movement on land. In non/stem amniotes, it is unbroken: temporal muscles inside solid roof of cheek or temporal region, when jaws close, muscles shorten and expand in breadth, leaving little room for expansion under shield. Vertebrae: amniotes have increase flexibility/movement, two anterior vertebrae modified, atlas and axis, birds/mammals, cranium-atlas and atlas-axis articulate for up/down side/side move. Increased feeding opportunities: reposition of head improves use of sensory organs. Changes to girdles/limbs of tetrapods, how they altered/improved land locomotion. Reduction number of bones in pectoral girdle. Archosaurs (birds/mammals), elbows rotate backwards, knees forward. Improved anchorage of hind limbs + increased attachment to pelvic girdle. Limbs move below body, more efficient support faster movement: faster, efficient locomotion. Papilli have differential growth, cells on anterior outer surface grow faster than posterior inner. Thick layer of keratin reduces water loss, less dependent on environment.