abomasum acetylcholine acid active transport adenosine triphosphate adipose tissue alcohol amylase anaerobic digestion anus ascending colon bicarbonate bile bile acid blood bolus carbon dioxide cardia cecum cellulose cephalic phase cerebral cortex cholecystokinin cholesterol chylomicron chyme chymotrypsin circulatory system d cell defecation descending colon dietary fiber diffusion digestive enzyme disaccharide duodenum emulsion enzyme epiglottis esophagus evolution fat feces g cell gallbladder gastric acid gastric glands gastric juice gastrin gastrointestinal tract gizzard glucagon glucose glycogen glycoprotein hepatic portal vein histamine hydrochloric acid hydrogen hydrolysis hyperglycemia hypoglycemia hypothalamus ingestion innate immune system insulin intestinal villus intrinsic factor lactase lacteal lactose large intestine larynx lipase liver maltase maltose mammal mastication medulla oblongata microvillus monosaccharide mouth neutralization nutrition oropharynx osmosis ph pancreas pancreatic duct pancreatic juice parietal cell pepsin peristalsis polysaccharide pons portal vein pylorus rectum ruminant saliva secretin sigmoid colon small intestine smooth muscle somatostatin starch stomach subclavian vein submucosa substrate sucrase sugar swallowing sympathetic nervous system thoracic diaphragm thoracic duct tongue transverse colon trypsin vagus nerve vertebrate vertebrate trachea