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Comparative Vertebrate Physiology An overview of digestion Feeding strategies Filter feeders Marine mammals and birds Feeding strategies Seizing of prey Why have a digestive tract? Unicellular animals digest intracellularly Disadvantages Limits size of prey Each cell must be designed to undertake digestion Extracellular (vertebrates) Allows the ability to feed on larger prey Only certain cells can digest Overview Anatomical areas Headgut (mouth, pharynx) Foregut (esophagus, stomach) Midgut (small intestine) Hindgut (colon) Functions 1. Ingestion – mouth 2. Motility Maintain muscle tone A. Propulsive movement: unidirectional B. Mixing movement: bidirectional Functions 3. Digestion • Mechanical Mouth (chewing), stomach (churning), small intestine (segmentation) • Chemical Passage across plasma membranes Carbohydrates: tri-, disaccharides to monoProteins: into amino acids Fats: monoglycerides and fatty acids Functions 4. Secretion Mouth, stomach, liver, pancreas, small intestine 5. Absorption 80% in the duodenum, rest in small and large intestine 6. Elimination of wastes Accessory glands Salivary glands Moisten, lubricate, breakdown saccharides Pancreas Enzymes secreted into duodenum Liver Neutralizes stomach acid, breakdown fats Gall bladder Store of bile Absorption Intestinal villi and microvilli