BIOL 2001 Lecture Notes - Lecture 9: Premolar, Rachis, Polyphyodont
11 Mar 2016
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Document Summary
Gives rise hairs, feathers, baleen, claws, horns, beaks, and some scales. Dermis and epidermis are separated by the basement o o o o. The dermis oten gives rise to dermal bones which gives rise to dermal scale. Placoid scales formed in dermis but project to the surface o. Scales help maintain a laminar low of water around the ish as it swims. Most important part of the dermis is the scale. Some have ctenoid scales while some have cycloid scales. Epidermis typically covered in mucus (mucus cuicle) o. Resists penetraion of bacteria, improves locomoion, someimes includes chemical defense against predators. Some have ganoid scales (gars) or lack scales (cafish) Scales have periods of growth and arrest, which allows you to age the ish based of the number of growth lines on the scale. Skin is used as a gas exchange surface (cutaneous respiraion) Presence of capillary beds in the dermis and epidermis. Skin of adults includes mucus and poison glands.
