<p> Animal Nutrition and… The Digestive System! -Luke Cheng</p><p>Part I: Food Four different feeding mechanisms: Suspension feeders: sift through water to obtain food (example: whales) Substrate feeders: you live on what you eat (example: caterpillars) Fluid feeders: you only drink stuff (mosquitoes, spiders, infant humans) Bulk feeders: you eat large pieces of food (snake swallowing an entire antelope)</p><p>Glucose regulation (two enzymes from pancreas, an example of homeostasis): Insulin--> causes liver and muscles to store glucose as glycogen Glucagon--> causes the breakdown of glycogen into bloodstream</p><p>Things that animals GOTTA EAT: Essential amino acids: Methionine, Valine, Threonine, etc. (lack of it: protein deficiency) Essential Fatty Acids: unsaturated fatty acids such as linoleic acid Vitamins (13 of them, these are ORGANIC nutrients): Water soluble:</p><p>B1(thiamine): coenzyme used in removing CO2 from organic compounds</p><p>B2(riboflavin): Component of coenzymes FAD and FMN Niacin: coenzyme component</p><p>B6(pyridoxine): coenzyme in amino acid metabolism Pantothenic acid: coenzyme again Folic acid (folacin): found in veggies, coenzyme for digestion</p><p>B12: coenzyme Biotin: coenzyme for fat synthesis Vitamin C: found in veggies, antioxidant, collagen synthesis, iron absorption, lack of it leads to scurvy Fat soluble vitamins: A(retinol): visual pigments, maintenance of skin tissue, antioxidant D: helps calcium and phosphorous absorption, promotes bone growth Lack of this stuff leads to rickets in children E(tocopherol): antioxidant, helps prevent damage to cell membranes K(phylloquinone): for blood clotting</p><p>Minerals (Inorganic nutrients, there are lots of them…): Calcium, Phosphorus: bone growth Sulfur: amino acid component Potassium: acid-base balance, nervous system Chlorine, Sodium, Magnesium… Iron: component of hemoglobin Fluorine: for your teeth (and maybe bones) Zinc, Copper, Manganese, Iodine: thyroid hormones Cobalt, Selenium, Chromium, Molybdenum… Part II: Extracellular digestion in other animals Earthworms: Mouth-Pharynx(throat)-Esophagus-crop-gizzard-intestine-anus(lol) Grasshoppers: Mouth-crop-“gastic ceca”(weird pouches extending from midgut)-rectum-anus Birds: Mouth-esophagus-Crop-stomach-gizzard-intestine-anus (Gizzards contain sand that pulverizes food before going into the intestine) Complete digestive tract/alimentary canal: a digestive tube extending between mouth and anus</p><p>Part III: The Human digestive system! Oral cavity: salivary glands secret salivary amylase, which digests starches, teeth mash food Epiglottis: a flap that blocks either windpipe or esophagus. Esophagus: uses peristalsis (rhythmic waves of contraction by smooth muscles) to move food Stomach: bolus of food gets churned in gastric juices, forms acid chyme, a mix of juice and food Pepsinogen: inactive form of pepsin that is first secreted, then activated by acid (HCl) Pepsin: hydrolysis of proteins into smaller polypeptides Small Intestine: 6 meters long, enzymatic digestion, most absorption of nutrients. Duodenum: chyme goes through pyloric sphincter into first segment of the s. intestine Helper organs: they secrete enzymes that digest macromolecules in the duodenum Pancreas: Chymotrypsin and trypsin, which breaks down proteins Also secretes other proteases (suffix “-peptidase”): Dipeptidase, carboxypeptidase, aminopeptidase. Gallbladder: stores bile, which emulsifies fats into small micelles Liver: produces bile. Jejunum and then Ilium: absorbs nutrients using huge surface area created by villi (little finger-like protrusions, and microvilli, which are ultra-tiny protrusions). Note that all nutrient-rich blood goes down the hepatic portal vein to the liver first.</p><p>Large intestine: absorbs water, mostly, has cecum and appendix, both useless in humans Rectum: stores your feces until you have a bowel movement (also stores bacteria like E. coli) Anus: no digestive functions here, this is just a sphincter (a muscular ring-like valve) that lets feces fall out.</p>