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Download Digestive System - Fall River Public Schools
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Digestive System Honors Biology Facilitator: Mr. Lee Room 320 Objective • Identify the major organs of the digestive system • Describe the function of the digestive system Introduction • The digestive system breaks down food into small molecules that can be passed to the cells that need them • The human digestive system is built around an alimentary canala one-way tube that passes through the body • Also called the Gastrointestinal Tract Digestive System Introduction… • The digestive system includes: • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Salivary glands, pancreas, and liver add secretions to the digestive system Mouth • Mechanical digestion: • Chewing begins mechanical digestion • Increases the surface area • The physical braking down of the food • Chemical digestion: • Starts in the mouth too • Digestive enzymes begin to break down carbohydrates into smaller molecules Mouth… • Different types of teeth: • Incisors: • Cut the food • Cuspids • Bicuspids • Molars: • Grind the food Mouth… • Saliva: • Saliva is a mixture of water, mucus, and amylase • Salivary glands secrete saliva • Helps to moisten the food and make it easier to chew • Release is controlled by the nervous system Mouth… • Saliva: • Breaks down chemical bonds in starches and releases sugars • Contains an enzyme called lysozyme; fights infections by digesting the cell walls of some bacteria The Esophagus • The chewed food (bolus) is forced into the pharynx when you swallow • The epiglottis prevents the food from entering the trachea • The pharynx is connected to the esophagus The Esophagus … • Esophagus has two muscle layers • Circular layer that wraps around the esophagus • Longitudinal layer that runs the length of the tube • Peristalsis is the rhythmic muscular contractions and relaxations that force the bolus to the stomach Stomach • Involved in both mechanical and chemical digestion • Has three layers of smooth muscle that twist and turn the stomach (mechanical digestion) • Circular layer • Longitudinal layer • Diagonal layer Stomach… • The inner lining of the stomach has gastric pits • Secrete mucus, enzymes, and hydrochloric acid • Forms the acidic mixture that is used in chemical digestion • pH is between 1.5 and 2.5 • The stomach is protected by mucus cells lining the stomach walls Review • Identify the organs of the digestive system: • Mouth • Pharynx • Esophagus • Stomach • Small intestine • Large intestine • Salivary glands, pancreas, and liver add secretions to the digestive system Review… • Describe the function of the digestive system: • The digestive system breaks down food into small molecules that can be passed to the cells that need them Learn Long Live Long
