BIOL 2312 Chapter Notes - Chapter 46: Osteoporosis, Hamstring, Unit
12 Sep 2017
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Hydrostatic skeletons use water pressure inside a body wall. Fluid filled cavity with circular and longitudinal muscles surrounding. Locomotion begins---> anterior circular muscles contract--> presses on fluid filled cavity---> front of body becomes thin---> chaeta pulled up---> anterior circulars relax---> longitudinal take over worm thickens in that space--> chaetae come down. Chintious frame work not as strong as internal bone fw. Insects breath through body so increase body mass means not enough oxygen. Endo skeletons are composed of hard internal structures: Cartilage and bone are living tissue (chitin is not) Bone can be classified by two modes of development: Bones from within a layer of connective tissue. Begins in region of the dermis---> dermis mainly mesenchyme---> mesenchyme cells can differentiate into osteoblasts---> osteoblasts arrange onto collagenous fibers---> secrete alkaline phosphatase---> calcium phosphate form crystalline configuration (hydroxyapatite)---> crystals merge along fibers to encase fibers.
