Lecture 7 - Nutrition and the digestion system

G teeth not all vertebrates share the same features eg

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Unformatted text preview: the outside environment –  Protects interior of cells from hydroly,c enzymes –  Can consume large food 31 Diges,on and absorp,on •  Gastrovascular cavity –  Simple extracellular diges,on –  One opening is entry and exit –  Diges,on and distribu,on of nutrients –  Food par,cles eventually phagocy,zed 32 Passive versus ac,ve absorp,on •  Nutrients must be absorbed by the epithelial cells lining alimentary canal •  Absorp,on methods –  Passive diffusion –  Facilitated diffusion –  Ac,ve transport •  Alimentary canal cells use some nutrients for their own needs but most transported into blood for the rest of the body 33 Tubular guts •  Mouth takes food •  Molecules are digested throughout the length of the gut •  Wastes are eliminated through the anus 34 Types of diges,on •  Food started to be fragmented in the mouth –  Teeth in vertebrates; radula in snails or mandibles in arthropods –  Gizzard, specialized por,on of the gut in bird to grind food –  Stomachs and crops are storage chambers that allows the inges,on of large amounts of food and digest it gradually •  Some animals (e.g. snakes) eats whole prey and gradually digest it 35 Absorp,on •  Most diges,on occurs in the intes,ne –  Water, ions and nutrients are absorbed across its walls –  Colon (large intes,ne) recovers water and ions and stores undigested waste (feces) –  Endosymbio,c bacteria colonized the intes,nes •  Helps degrada,on of food •  In humans produce Vitamin K and bio,n –  Our gut contains 10 ,mes more bacteria than human cells •  In herbivores bacterial helps degrada,on of cellulose 36 Vertebrates gastrointes,nal system •  GI track plus accessory structures (e.g. teeth) •  Not all vertebrates share the same features (e.g. some fish do not have stomach and birds do not have gallbladder) 37 Vertebrates gastrointes,nal system •  Anterior end func,ons primarily in inges,on –  Oral cavity, salivary glands, pharynx (throat), and esophagus •  Middle por,on func,ons in storage and ini,al diges,on –  Upper part of small intes,ne and associated organs (liver, g...
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