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Lecture #18 Date ______

Lecture #18 Date ______. Chapter 41 ~ Animal Nutrition. Nutritional requirements. Undernourishment : caloric deficiency Overnourishment (obesity): excessive food intake Malnourishment : essential nutrient deficiency

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Lecture #18 Date ______

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  1. Lecture #18 Date ______ • Chapter 41 ~ Animal Nutrition

  2. Nutritional requirements • Undernourishment: caloric deficiency • Overnourishment (obesity): excessive food intake • Malnourishment: essential nutrient deficiency • Essential nutrients: materials that must be obtained in preassembled form • Essential amino acids: the 8 amino acids that must be obtained in the diet • Essential fatty acids: unsaturated fatty acids • Vitamins: organic coenzymes • Minerals: inorganic cofactors

  3. Food types/feeding mechanisms • Opportunistic • Herbivore: eat autotrophs • Carnivore: eat other animals • Omnivore: both • Feeding Adaptations • Suspension-feeders: sift food from water (baleen whale) • Substrate-feeders: live in or on their food (leaf miner) (earthworm: deposit-feeder) • Fluid-feeders: suck fluids from a host (mosquito) • Bulk-feeders: eat large pieces of food (most animals)

  4. Overview of food processing • 1-Ingestion: act of eating • 2-Digestion: process of food break down • enzymatic hydrolysis • intracellular: breakdown within cells (sponges) • extracellular: breakdown outside cells (most animals) • alimentary canals (digestive tract) • 3- Absorption: cells take up small molecules • 4- Elimination: removal of undigested material

  5. The Alimentary Canal • Primitive inverts have gastrovascular cavity – a digetive sac with a single opening, functions in digestion and distribution of nutrients (cnidarians and flatworms) • All others have an alimentary canal – a digestive tube extending between two openings, a mouth and an anus

  6. Mammalian digestion, I • Peristalsis: rhythmic waves of contraction by smooth muscle • Sphincters: ring-like valves that regulate passage of material • Accessory glands: salivary glands; pancreas; liver; gall bladder

  7. Mammalian digestion, II • Oral cavity: salivary amylase (hydrolyzes starch), bolus (ball of chewed food • Pharynx (the throat): epiglottis - a cartilagenous flap that moves up to cover the trachea (windpipe) during swallowing • Esophagus: conducts food from the pharynx to the stomach by peristalsis – an involuntary wave-like muscle contraction

  8. Mammalian digestion, II cont. • Stomach – stores food and performs preliminary steps of digestion • Churning and enzymes convert food to nutrient broth called acid chyme • Secretion of enzymes – controlled by nerve impulses and hormone gastrin • 3 types of secretory cells: • Mucous cells, secrete mucin (thin mucus layer protects stomach lining) and gastrin (stimulates further secretion of gastric juice) • Chief cells, secrete pepsinogen (inactive precursor of pepsin) • Parietal cells, secrete HCl • gastric juice (HCl and pepsin) • HCI- acidity (pH 1-4) kills bacteria, starts conversion of pepsinogen to pepsin • pepsin – begins to split peptide bonds of large polypeptide chains

  9. Mammalian digestion, III • Small intestine – more than 6 m in humans, where most enzymatic hydrolysis and absorption of nutrients occurs • 3 sections – duodenum, ileum, jejunium • In duodenum the acid chyme mixes with digestive juices from the pancreas, liver, gall bladder, and the intestinal wall • Pancrease – protease for protein digestion and bicarbonate to buffer the acid chyme • Liver – bile for fat emulsification (stored in the gall bladder)

  10. Mammalian digestion, III cont.

  11. Mammalian digestion, IV • Villi (large circular folds) contain microvilli – increase surface area to increase nutrient absorption; each villus contains microscopic blood vessels (capillaries) and a lacteal (a small lymphatic vessel) • Nutrients are absorbed across the intestinal epithelium and across the epithelium of the capillaries or lacteal • Hepatic portal vein – carries nutrient rich blood away from villi directly to the liver (can interconvert various organic molecules)

  12. Hormonal Action: gastrin – stomach, gastric juice production secretin – small intestine, stimulates pancreas to release buffer cholecystokinin (CCK) – small intestine, triggers release of bile from gall bladder enterogastrone – small intestine, assists in fat hydrolysis Large intestine (colon) – site of water absorption Cecum Appendix Feces Rectum/anus Mammalian digestion, V

  13. Evolutionary adaptations • Dentition: an animal’s assortment of teeth • Digestive system length • Symbiosis • Ruminants

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