1 Chapter 41 ~ Animal Nutrition 2 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) 3 Homeostasis Digestion Example Glucose Regulation - 90mg glucose/100ml blood Levels rise = insulin produced to move glucose into cells (muscle/liver) Levels drop = glucagon produced stimulates release of glucose from muscle/liver Undernourishment: caloric deficiency Overnourishment (obesity): excessive food intake 4 Nutritional requirements Malnourishment: essential nutrient deficiency Essential nutrients: materials that must be obtained in pre-assembled 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 55 6 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 7 Mammalian digestion, I Peristalsis: rhythmic waves of contraction by smooth muscle Sphincters: ring-like valves (smooth muscle) that regulate passage of material Accessory glands: salivary glands; pancreas; liver; gall bladder About 30 ft! 8 The Oral Cavity Teeth cut, smash, and grind food into smaller pieces with a larger surface area. Salivary Glands release saliva (more than one liter per day!) after being stimulated. Parotid Submandibular Sublingual Saliva contains mucin (a slippery glycoprotein), antibacterial agents, and salivary amylase (breaks down starch and glycogen) Tongue is responsible for tasting and shaping food into a ball shape called a bolus. Also a skeletal muscle! Lips and Cheeks, composed of skeletal muscle, form boundary. The Pharynx - Opens to Esophagus and Trachea (windpipe) - The Glottis, visible as the Adams Apple, is covered by a flap (epiglottis) to prevent passing food from going down the wrong pipe. The Esophagus (25 cm long). [Lined with stratified squamous] - controls the passage of food from the pharynx to the stomach by Peristalsis, rhythmic waves caused by muscle contractions - Esophageal Sphincter is a ring shaped stopper between the pharynx and esophagus. The Pharynx and Esophagus 10 11 - Stomach Folded, elastic and can hold about two liters of food and fluid! Gastric juice - secreted by epithelium that lines stomach walls. 12 Gastric Pits Parietal Cells: secrete HCl making stomach contents pH 1.5 3.5 Chief Cells: secrete pepsinogen which become activated (by removal of small peptide, exposing active site) by HCl to become pepsin. Can also be activated by pepsin. Mucus coats the stomach wall for protection, prevents leakage of chyme between cells, damaged cells quickly shed and replaced. Surface epithelium renewed every 3-6 days! 13 Functions of Hydrochloric Acid in Gastric Juices Acid disrupts extracellular matrix that keeps cells together in meat and plant material Kills most bacteria swallowed with food Activates pepsinogen Gastric secretions controlled by hormone Gastrin. Gastrin released by aroma, sight, thought of food and by food reaching the stomach 3 Liters/day! 14 Passing through the Stomach -A bolus will come to the stomach from the esophagus by way of peristalisis -The stomach churns and mixes, and in cooperation with enzymes, creates acid chyme -From here, the chyme goes through the pyloric sphincter into the small intestine. 15 Mammalian digestion, III Small intestine - hydrolysis and absorption duodenum bile Intestinal digestion: carbohydrate, fat, protein, nucleic acid Please notice where each type of molecule is digested 16 The Duodenum 17 Mammalian digestion - small intestine Villi / microvilli- increase absorption (How??) Lacteal (lymphatic) Chylomicrons (fats mixed with cholesterol) Hepatic portal vessel - Blood goes to liver for processing 3-6 hrs for chyme to travel through sm. intestine 18 Mammalian digestion - Hormones Hormonal Action: Gastrin food---> stomach wall ---> gastric juice Enterogastrones (duodenum) 1-Secretin acidic chyme ---> pancreas to release bicarbonate 2-Cholecystokinin (CCK) amino/fatty acids ---> pancreas to release enzymes and gall bladder to release bile Regulate running of digestive system 19 Mammalian Digestion - Large Intestine (colon) 19 Is connected to small intestine at a pouch called the cecum (aka. Appendix) Function - reabsorb water from digestion Movement from paristalsis Bacterial flora consume cellulose and produce about 500 ml of dimethyl sulfide, H 2, N 2, CH 4, and CO 2 ; aka flatus. Also synthesize vitamin K to be used by liver. Rectum - storage/end of colon Anus - opening between voluntary and involuntary sphincters 20 Structural Adaptations to Diet - Dentition 1. Carnivores have large canines and incisors 2. Herbivores have small canines 3. Omnivores have medium sized everything 21 Structural Adaptations Due to Diet -Length of digestive system 1. Carnivore is smaller 2. Herbivore is longer due to cell walls - Ruminant digestion symbiosis