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The Digestive System A guide to Chapter 16 Digestion of Food Food must be broken down into nutrients in a process known as digestion. The breaking down of food into simpler substances for use by the body is the work of the digestive system. Types of Digestion Chemical Digestion: The digestion by enzymes and other chemicals. Enzymes: are chemicals that control chemical reactions in the body. Mechanical Digestion: The physical action of breaking down food into smaller parts (chewing). Absorption: When nutrients and water are absorbed through the villi and blood vessels. Steps of Digestion The Mouth: Mechanical Digestion: chewing. Chemical Digestion: Saliva contains ptyalin an enzyme that breaks down starch and changes it into sugar. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Esophagus Means “to carry what is eaten”. Lined with mucus. Peristalsis: powerful waves of muscle contractions that pushes the food downward to the stomach. Stomach Chemical Digestion: Gastric Juices contains the enzyme pepsin, hydrochloric acid and mucus. Pepsin and HCl break down proteins. Mechanical Digestion: Muscle contractions and peristalsis. QuickTi me™ and a TIFF ( Uncompressed) decompr essor are needed to see thi s p icture. Secondary Organs These organs help in digestion. They also have other roles in the body. Liver Gallbladder Pancreas QuickTime™ and a TIF F (Uncompressed) decompressor are needed to see this picture. Liver The body’s largest and heaviest internal organ. Produces bile Bile breaks up large fat molecules. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Gallbladder Small organ under the stomach. Stores bile produced by the liver. Releases bile through a duct or tube as the food moves into the small intestine. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Pancreas Soft, triangular organ located between the stomach and the small intestine. Produces pancreatic juices which is a mixture of several enzymes. Pancreatic juices break down proteins, starches and fats. Produces insulin, which controls the body’s sugar levels. QuickTime™ and a TIFF (U ncompressed) decompressor are needed to see t his picture. Small intestine 2.5 centimeters in diameter, 6 meters long. Most chemical digestion takes place in the beginning of the small intestine. Digested food is absorbed through the villi into a network of blood vessels. QuickTime™ and a TIF F (Uncompressed) decompressor are needed to see this picture. Large Intestine Water is absorbed here. Helpful bacteria live in the large intestine and make vitamin K and B complex. 6.5 centimeters in diameter and 1.5 meters long. Rectum stores waste products. Anus is the opening that releases the solid wastes. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. The End By Mrs. Scibelli Prentice Hall, Exploring Life Science QuickTime™ and a TIF F (Uncompressed) decompressor are needed to see this picture.