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Chapter 3 Digestion, Absorption, Transport Food must be digested in order to be useful to the body. Digestion What is the basic anatomy of the GI tract? mouth → esophagus → stomach → small intestine → large intestine → rectum → anus GI Tract Anatomy Epiglottis Trachea Esophagus Esophageal sphincters Stomach Pyloric sphincter Appendix Salivary glands Pharynx Epiglottis Lower esophageal sphincter Esophagus Trachea (to lungs) Pancreas Pancreatic duct Stomach Pancreas Pancreatic duct Small intestine (duodenum, jejunum, ileum) Liver Bile duct Ileocecal valve Ileocecal valve (sphincter) Mouth Upper esophageal sphincter Gallbladder Pyloric sphincter Small intestine Anatomy Appendix Liver Rectum Gallbladder Anus Bile duct Large intestine (colon) Large intestine (colon) Rectum Anus ELIMINATION Fig. 3-1, p. 73 Close-Up View of the Organs of the Digestive System Gland A cell or group of cells that secrete a substance that the body requires Types of Glands Exocrine Glands: secrete their materials “out” (into the GI tract or onto the skin) Endocrine Glands: secrete their materials “in” (into the blood) Head Salivary glands Fig. 3-5, p. 76 Bolus The portion of food which is swallowed at one time pH The unit of measure expressing a solution’s relative acidity or alkalinity pH of common substances: Basic Concentrated lye pH Oven cleaner Household ammonia pH neutral Baking soda Bile Pancreatic juice Blood Water Saliva Urine Coffee Orange juice Vinegar Lemon juice Gastric juice Acidic Battery acid Fig. 3-6, p. 77 Chyme The semi-liquid mass of partially digested food that is expelled from the stomach into the duodenum Picture Longitudinal Circular Diagonal Fig. 3-2, p. 75 Picture Esophagus Circular muscle Longitudinal muscle Esophagus muscles relax, opening the passageway. Stomach Diaphragm muscles relax, opening the passageway. Esophagus muscles contract, squeezing on the inside. Diaphragm muscles contract, squeezing on the outside. Fig. 3-4, p. 76 Esophagus Picture Reflux Diaphragm Weakened lower esophageal sphincter Stomach Acidic stomach contents Gastroesophageal Reflux Fig. H3-4, p. 96 Peristalsis Successive waves of involuntary muscular contractions passing along the length of the GI tract Peristalsis The small intestine has two muscle layers that work together in peristalsis and segmentation. Circular muscles are inside. Longitudinal muscles are outside. Fig. 3-3a, p. 75 Details of Peristalsis PERISTALSIS Chyme The inner circular muscles contract, tightening the tube and pushing the food forward in the intestine. When the circular muscles relax, the outer longitudinal muscles contract, and the intestinal tube is loose. As the circular and longitudinal muscles tighten and relax, the chyme moves ahead of the constriction. Fig. 3-3b, p. 75 Details of Segmentation SEGMENTATION Chyme Circular muscles contract, creating segments within the intestine. As each set of circular muscles relaxes and contracts, the chyme is broken up and mixed with digestive juices. These alternating contractions, occurring 12 to 16 times per minute, continue to mix the chyme and bring the nutrients into contact with the intestinal lining for absorption. Fig. 3-3c, p. 75 Please click out of WebCT and go to the following website to learn more about heartburn and other GI problems. http://www.gihealth.com