Digestive System Definitions Digestion the mechanical and chemical breakdown of food into subunits so that nutrients can be absorbed Ingestion the act of taking food into the mouth Digestive Tract the central pathway of the digestive system a long muscular tube that pushes food between the mouth and the anus Salivary Glands glands that secrete enzymes including salivary amylase which digests carbohydrates into the mouth Tongue a muscular organ in the mouth that aids swallowing Esophagus the sections of the digestive tract between the mouth and the stomach Peristalsis coordinated muscular contractions that force food down the digestive tract Stomach an expandable muscular organ that stores mechanically breaks down and digests proteins in food Pepsin a protein digesting enzyme that is active in the stomach Chyme the acidic soup of partially digested food that leaves the stomach and enters the small intestine Small Intestine the organ in which the bulk of chemical digestion and absorption of food occurs Duodenum the first portion of the small intestine the duodenum receives chyme from the stomach and mixes it with digestive secretions from other organs Pancreas an organ that helps digestion by producing enzymes such as lipase that act in the small intestine and by secreting a juice that neutralizes acidic chyme Liver an organ that aids digestion by producing bile salts that emulsify fats Bile Salts chemicals produced by the liver and stored by the gallbladder that emulsify fats so that they can be chemically digested by enzymes Emulsify to break up large fat globules into small fat droplets that can be more efficiently chemically digested by enzymes Gallbladder an organ that stores bile salts and releases them as needed into the small intestine Lipase a fat digesting enzyme active in the small intestine Epithelial Cells cells that line organs and body cavities in the digestive tract they sit in direct contact with food and its breakdown products Absorption the uptake of digested food molecules by the epithelial cells lining the small intestine Villi Singular Villus fingerlike projections of folds in the lining of the small intestine that are responsible for most nutrient and water absorption Large Intestine the last organ of the digestive tract in which remaining water is absorbed and solid stool is formed Colon the first and longest portion of the large intestine the colon plays an important role in water reabsorption Stool solid waste material eliminated from the digestive tract Elimination the expulsion of undigested matter in the form of stool
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