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Animal Nutrition Essential Nutrients: required by cells, obtained through foodFour classes of essential nutrients:· Essential amino acids (8)· Essential fatty acids· Vitamins (13) - fat-soluble, water-soluble· Minerals Dietary DeficienciesUndernourished: diet is deficient in calories, not enough energyMalnourishment: missing 1+ essential nutrients The main stages of food processing:Ingestion: eatingDigestion: breakdown of food into small molecules· Mechanical (chewing, grinding)· Chemical (enzymes)Absorption: cells take up nutrientsElimination: pass undigested materials from digestive system Digestive compartments:Most animals process food in specialized compartmentsIntracellular: digestion of food inside cells by food vacuoles Ex. phagocytosis, pinocytosis, spongesExtracellular: food broken down outside of cells Gastrovascular cavity (simple) or alimentary canal (complex) Compartments are outside of the animal’s body Gastrovascular cavity: simple animals; single-opening, 2-way digestion (food in, waste out)Alimentary canal: more complex, one-way tubes with mouth and anus Specialized organs for digestion in Humans Digestive system = alimentary canal + glands Glands = salivary glands, pancreas, liver, and gallbladder Q: Can you name the organs of the human alimentary canal in order? Peristalsis: push food through rhythmic contractions of muscles in the wall of the canalSphincters: valves regulate the movement of material between compartments Digestion of Macromolecules: Mouth = carbs Stomach = proteins Small Intestine = carbs, proteins, fats, nucleic acids Digestion in the Mouth· Oral cavity: mechanical, chemical digestion· Salivary glands: saliva lubricates food· Teeth chew food into smaller particles· Salivary amylase: breakdown glucose polymers· Saliva contains mucus, a viscous mixture of water, salts, cells, and glycoproteins· Pharynx: back of throat· Epiglottis: flap of cartilage, covers trachea when swallowing· Esophagus: food tube (pharynx à stomach)Digestion in the Stomach· Stomach stores food and secretes gastric juice, converting a meal to acid chyme· HCl: pH 2, kills bacteria & denatures proteins· Pepsin: an enzyme (protease) that hydrolyze proteins into smaller peptideso Pepsinogen (inactive) à pepsin (active) by HCl· Mucus: protects lining of stomach· Gastric ulcers: lesions in the lining, caused mainly by bacterium Heliobacter pylori Digestion in the Small Intestine· SI = major organ of digestion and absorptiono Duodenum: first section, digestive juices, major chemical digestion· Digestive juices:o Pancreas: bicarbonate (basic), trypsin & chymotrypsin (proteases); lipase (fats); amylase (carbs); nuclease (DNA, RNA)o Bile: made in liver, stored in gall bladder§ Emulsify fats (make smaller droplets) Hormones that coordinate digestion:· Gastrin: produced by stomach, éproduction of gastric juices· Entrogastrin: produced by SI (duodenum), êperistalsis to allow time for fat digestion· Secretin & CCK (cholesystokinin): secreted by SI (duodenum), éflow of digestive juices from pancreas & gall bladder Absorption in the Small IntestineVilli and microvilli increase surface area Villi à capillaries à hepatic portal vein à liver à heartLiver: distribute nutrients, detox, glucose storage (glycogen) Absorption in the Large Intestine LI = colon Function = compact waste, reabsorb water Cecum: pouch where SI & LI meet, ferment plant material Appendix = extension of cecum, role in immunity Rectum: end of LI, feces stored until elimination Evolutionary adaptations of vertebrate digestive systems correlate with dietDentition: teeth correlate with diet· Herbivores: longer alimentary canal, longer cecum Mutualistic AdaptationsMany herbivores have fermentation chambers, where mutualistic microorganisms digest cellulose (ruminants) Homeostatic Mechanisms Vertebrates store excess calories as glycogen in the liver and muscle cells, and as fat in adipose tissue Overnourishment can lead to obesity Leptin: hormone, suppresses appetite
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