Chapter38 - Chapter 38 A. Skeletal Systems a. Hydrostatic...

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A. Skeletal Systems a. Hydrostatic Skeletons i. Many soft-bodied invertebrates have Hydrostatic Skeletons , which are made of fluid-filled compartments. ii. It works like a balloon filled with water. iii. Cnidarians, Flatworms, Roundworms, Annelids have them. iv. In the Hydra and other Cnidarians, the two body layers are capable of contracting. 1. The cells in the outer layer lie longitudinally, the ones on the inner layer lay are arranged circularly around the body cavity 2. They work in an antagonistic fashion, what one can do the other can undo. v. Hydrostatic skeletons allow only for crude mass movements of the entire body or appendages. vi. Delicate movements are difficult because the fluid that makes the skeleton tends to move in even amounts throughout the body. vii. Annelids have a more sophisticated type of hydrostatic skeleton. viii. Earthworm’s body has transverse sections or septa that divide the hydrostatic skeleton. ix. Starfish movement is done by a derived form of the hydrostatic skeleton. b. Exoskeletons i. In mollusks and arthropods the skeleton is a lifeless shell or an exoskeleton . ii. Mollusks calcium carbonate iii. Arthropods the polysaccharide chitin . iv. Joints provide the flexibility. v. To accommodate growth, arthropods must molt , or shed their exoskeleton and replace it with a larger one. c. Internal Skeletons i. Echinoderms and Chordates have an endoskeleton , a living internal skeleton made of calcium impregnated tissue. ii. Calcium is imbedded in the call wall of the cells in the skeleton. iii. Provides support and protection and transmits muscle force. iv. Some skeletons can be made of entirely cartilage. B. Muscle Contraction i. All eukaryotic cells contain the contractile protein actin, the major component of microfilaments. ii. In most cells actin is associated with myosin , a contractile protein. iii. These two proteins are most highly organized in muscle cells. b. A Vertebrate muscle may consist of thousands of muscle fibers i. In vertebrates, skeletal muscle is the most abundant form of tissue. ii.
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This note was uploaded on 04/02/2008 for the course BIO 101 taught by Professor Martin during the Spring '08 term at Rutgers.

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Chapter38 - Chapter 38 A. Skeletal Systems a. Hydrostatic...

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