digestion chapter 41 basic needs Nutritional Requirements A nutritionally adequate diet satisfies three needs: Fuel (chemical energy) organic raw materials organic carbon organic nitrogen Essential nutrients metabolic rates -- amount of energy used per unit time... calorie -- kilocalorie (Calorie) (kcal) basal metabolic rate -- (BMR) standard metabolic rate -- (SMR) energy budget budgets energy budget undernourishment overnourishment malnourishment 20 amino acids in animals 8 essential amino acids humans (histidine) Most plant proteins are incomplete vegetarian diets? Annual energy expenditure (kcal/hr) ENDOTHERMS 800,000 Basal Reproduction (standard) Thermoregulation metabolism Growth Activity 340,000 60-kg female human 4-kg male Adélie penguin from temperate climate from Antarctica (brooding) ECTOTHERM 8,000 4,000 0.025-kg female deer mouse 4-kg female eastern from temperate North America indigo snake ESSENTIAL AMINO ACIDS FOR ADULTS Corn (maize) and other grains Methionine Valine Threonine Phenylalanine Leucine Isoleucine Tryptophan Beans and other legumes Lysine
comparative Vitamins required in tiny amounts 13 essential vitamins in humans water-soluble vitamins and fat-soluble vitamins deficiencies? feeding mechanisms suspension feeding deposit feeding substrate feeding bulk feeding fluid feeding comparative comparative cnidarians/platyhelminthes/acoela extracellular digestion intracellular digestion gastrovascular Tentacles Food Mouth Gastrovascular cavity complete digestive tracts unidirectional -- stepwise digestion Crops and stomachs Gizzards intestine anus Pharynx Crop Gizzard Intestine Anus Mouth Typhlosole Lumen of intestine FOREGUT MIDGUT HINDGUT Rectum Anus Epidermis Gastrodermis Crop Mouth Gastric ceca
processing mouth Ingestion oral cavity, pharynx, and esophagus act of eating mechanical fragmentation (mastication) physical and mastication digestion absorption elimination venom snakes hemolytic venoms neurotoxic venoms spiders undigested undigested material material ingestion dentition tooth shape homodont vs. heterodont digestion absorption elimination Incisors Canines Premolars (a) Carnivore (b) Herbivore HOMODONT saliva HETERODONT (c) Omnivore Molars mucin protects from abrasion lubricates buffers mouth saliva is alkaline Antibacterial agents salivary amylase lingual lipase
ingestion Food pharynx -- glottis/epiglottis esophagus peristalsis. Tongue Pharynx Glottis Larynx Trachea To lungs To stomach Epiglottis up Esophageal sphincter contracted Glottis up and closed Epiglottis down Esophageal sphincter relaxed Glottis down and open Relaxed muscles Epiglottis up Esophageal sphincter contracted Contracted muscles stomach max volume about 2 L Gastric juice (gastrin) HCl pepsin Cardiac Sphincter Fundus Relaxed muscles Sphincter relaxed Pyloric Sphincter Stomach 5 µm Duodenum Rugae Interior surface of stomach Pylorus duodenum digestion and absorption disaccharidases -- epithelium nucleases - epithelium pancreas -- bicarbonate hydrolytic enzymes Pancreatic amylases protein digestion Trypsin, chymotrypsin Carboxypeptidase
Oral cavity, pharynx, esophagus liver - produces bile. bile salts - emulsification pigments stored in gallbladder Pepsin Stomach Lumen of small intestine Lingual lipase Salivary amylase Pancreatic amylases Pancreatic trypsin and chymotrypsin Pancreatic nucleases bile salts Pancreatic lipase Pancreatic carboxypeptidase Nucleotidases Epithelium of small intestine (brush border) hormonal control Dipeptidases, carboxypeptidase, aminopeptidase absorption enterogastrones secretin Cholecystokinin (CCK) Disaccharidases Gallbladder Bile jejunum and ileum (small bowel) Liver Stomach Secretin and CCK Gastrin CCK Pancreas Duodenum of small intestine Secretin CCK KEY Stimulation Inhibition 300 m2 lacteals Nucleosidases and phosphatases
hepatic portal vessel modifies mix large intestine cecum vermiform appendix 1.5 m long water absorption transverse colon descending colon liver absorption ascending colon absorption cecum rectum appendix vermiform apparatus intestinal flora -- (bacteria) Escherichia coli (O157:H7) hemolytic uremic syndrome generate gases CH4, H2S produce vitamins biotin (B7), folic acid(b9), vitamin K digestion of cellulose? sigmoid colon