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Nutrition and Digestion Organism S&F Tony Serino, Ph.D. Biology 201 Misericordia University Digestion • The reduction through mechanical and chemical means (hydrolysis) of complex food substances into simple monomers and their absorption into the internal environment. Nutrition Nutrition – the total process involved in acquiring and utilizing food substances for growth, repair, maintenance and activities in living organisms Nutritional Modes: Herbivore –primarily plant eater (eats producers) Carnivore –primarily animal eater (eats consumers) Omnivore –eats both plant and animals Match the animal with its mode. Feeding Mechanisms • Suspension feeders –feeds by eating food particles suspended in water (includes filter feeding) • Substrate feeders –animals that live in or on their food • Fluid feeders –suck nutrients from living organism • Bulk feeders –eat relatively large chunks of food Diet • Are the types of foods acquired by the organism • Must satisfy the needs of the organism for energy, building blocks (carbon and nitrogen), and essential nutrients • Essential Nutrients –are materials the animal cannot synthesize but are required for normal function; includes: minerals and certain organic compounds Essential Nutrients • Essential Amino Acids –amino acids that cannot be synthesized by the organism (Humans have 8 essential AA). Meat, cheese and eggs are complete sources of these AA • Essential Fatty Acids –FA needed by organism; found in seeds, grains, and vegetables • Vitamins –organic compounds used to complete protein structures (cofactors) or coenzymes, required in small quantities • Minerals –inorganic molecules required in very small amounts, serve a wide variety of purposes Deficiencies can cause malnutrition; overdose can cause toxic effects Functions of Digestive System • Motility(Propulsion) – Ingestion –food enters tract – Mastication -chewing – Deglutition -swallowing – Transportation through tract (peristalsis) – Mixing (churning, segmentation) – Egestion (Defecation) • Secretion – Endocrine and Exocrine secretions • Digestion – mechanical and chemical breakdown of food • Absorption – Passage of food particles from external to the internal environment Tube Movements Peristalsis Segmentation* *majority of contractions of SI Simple Digestive System: Gastrovascular Cavities • Seen in some flatworms and cnidarians; has only one opening • Used for both digestion and transportation of nutrients to its tissues • Sometimes referred to as an Incomplete Gut (Complete guts have mouth and anus) Major Organs of System Accessory Organs Teeth Mouth –ingestion, mastication, mechanical dig. Salivary glands secrete saliva –mixture of water, mucus, electrolytes, antibodies and enzymes. Enzymes are salivary amylase (pytalin) which breaks down starches and maltase. Tongue –mixes food and tastes Teeth –mechanical digestion Teeth Functionally allows the acquisition, grinding and chopping of food Specialization allows for different food ingestion Dental formula for adult human: (2,1,2,3) Tooth Anatomy Odontoblasts –secrete dentin Ameloblasts –secrete enamel Deglutition (Swallowing) Peristaltic contractions in pharynx and esophagus transport food to stomach Stomach • J-shaped muscular pouch • Receives bolus and produces chyme • Liquefies food by mixing it with HCl and vigorous churning • Produces gastric juice: mucous, water, HCl, enzymes in some animals, some factors necessary for vitamin absorption ( in humans, GIF binds to vit. B12 in diet) • Low pH stops amylase activity, but secretes pepsinogen (pepsin) that begins break down of proteins • Absorbs little except imbibed water, electrolytes, and some drugs (ie. alcohol and aspirin) Crop and Gizzard • Additional storage or grinding areas associated with the esophagus and stomach, respectively • Crops are specializations of the esophagus that temporarily store large amounts of food; allowing for quick intake in short amounts of time Gizzards –highly muscular thick walled extension of stomach used to grind coarse food; the animal swallows small rocks that are retained in the gizzard to grind the food into a paste Ruminants • Have four chambered stomach for digestion of plant fibers Rumen –temporary storage and largest segment of stomach Reticulum –this and the rumen contain large numbers of bacteria and protists that break down cellulose; forms the “cud” Omasum –removes water from thoroughly masticated cud Abomasum –final enzymatic breakdown of cud with stomach’s own enzymes Ruminant eats grass with little chewing and swallows large quantities down to the rumen. There the plant matters is mixed with mucus and enzymes produced by bacteria in the rumen. At intervals, some of the contents pass to the reticulum where fermentation continues. The reticulum forms boluses (cuds) that can be regurgitated for further mastication. This may be repeated several times. Eventually some of this well masticated mash passes to the omasum where water reabsorption takes place before the food mass passes to the abomasum (the true glandular portion of the stomach) where additional gastric enzymes are added to produce chyme. Small Intestine • Largest amount of digestion and absorption of gut; usually divided into 3 sections: doudenum (neutralizes chyme and receives secretions of liver and pancreas), jejunum (bulk of digestion, & ileum (bulk of absorption) • Several structures to increase surface area: plica, villli, length, microvilli • Secrete or have bound enzymes that complete digestion process • Intestinal juice also contains mucous and antibacterial compounds • Absoprtion directly into capillary bed of villi or into villus lacteal Herbivore vs. Carnivore SI • Herbivores have – Longer intestine – Large cecum houses bacteria used in digesting vegetation • Carnivores have: – Larger, more expandable stomach relative to body size Large Intestine (colon, cecum & rectum) • Massive re-absorption of water and electrolytes by active absorption of Na+ • Microbe action produces Vit. K, biotin, folic acid and is absorbed by LI • Responsible for egestion (defecation reflex) Liver • • • • • Metaboblizes all food groups Storage of Fe and Cu and other metals Storage of Vit. A, B12, D, E, K Produces bile and most plasma proteins Detoxifies the blood, storage of toxins Bile Salts Up to 95% of the cholesterol-based bile salts are “recycled” by reabsorption along the intestine. Pancreas • Heterocrine gland secretes pancreatic juice and hormones • Pancreatic juice is sodium bicarbonate and digestive enzymes including trypsin, chymotrypsin, carboxypeptidase, lipase, etc. • Hormones: insulin, glucagon, somatostatin Arterial Flow to Viscera Celiac a. Sup. Mesenteric a. Inf. Mesenteric a. Hepatic Portal System Portal vein Superior Mesenteric v. Splenic v. Inferior Mesenteric v.