01:119:117 Lecture Notes - Lecture 10: Facilitated Diffusion, Active Transport, Phagocytosis
19 Dec 2017
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Dont go free throughout cytosol: ex: sponges, extracellular digestion- break down food in organs that are continuous with the outside of the body, gastrovascular cavity- single opening in animals with a simple body plan. The mouth = anus ex: cnidarians: alimentary canal- (complete digestive tract) one way tube with two openings on each side, well organized ds, the accessory glands, three pairs of salivary glands, the pancreas, the liver, the gallbladder. Food is pushed along the alimentary canal by peristalsis- waves of contraction and relaxation in the smooth muscles of the canal. At some of the junctions the muscular layer forms ring-like valves known as sphincters- they act like drawstrings to regulate the passage of materials between the compartments in the canal. Why doesn"t the gastric juice destroy the stomach itself: works in a very acidic environment. Ii. cleaves proteins into even smaller polypeptides: further digestion of amino acids happens in the si.
