ch17_answer_key - Shier, Butler, and Lewis: Holes Human...

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Shier, Butler, and Lewis: Hole’s Human Anatomy and Physiology, 10 th ed. Chapter 17: Digestive System Chapter 17: Digestive System I. Introduction A. Digestion is the breakdown of foods into forms that cell membranes can absorb. B. Mechanical digestion breaks large pieces of food into smaller ones without altering their chemical composition. C. Chemical digestion breaks down food into simpler chemicals. D. The organs of the digestive system carry out the processes of ingestion, propulsion, absorptions, defecation, and digestion. E. The alimentary canal is composed of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anal canal. F. The accessory organs of the digestive system are salivary glands, liver, gallbladder, and pancreas. II. General Characteristics of the Alimentary Canal A. Introduction 1. The alimentary canal is a muscular tube that passes through the body’s ventral cavity. 2. The structure of its wall, how it moves food, and its innervation are similar throughout its length. B. Structure of the Wall 1. The four layers of the alimentary wall are the mucosa, submucosa, muscular layer, and serosa. 2. The mucosa is located as the inner lining and is composed of epithelial tissue, a small amount of connective tissue, and some smooth muscle. 3. The functions of the mucosa are to secrete mucus and enzymes, and to absorb nutrients. 4. The submucosa is located deep to the mucosa and is composed of loose connective tissue, glands, blood vessels, lymphatic vessels, and nerves.
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5. The functions of the submucosa are to nourish surrounding tissues and to carry away absorbed substances. 6. The muscular layer is located between the submucosa and serosa and is composed of two coats of smooth muscle tissue. 7. When the circular fibers contract, the diameter of the tube decreases. 8. When the longitudinal fibers contract, the tube shortens. 9. The serosa layer is located superficial to the muscular layer and is composed of the visceral peritoneum. 10. The functions of the serosa are to moisten and lubricate the outside of the organ. C. Movements of the Tube 1. The two types of motor functions of the alimentary canal are mixing and propelling. 2. Mixing occurs when smooth muscles in small segments of the tube contract rhythmically. 3. Peristalsis is a wavelike motion. 4. Peristalsis occurs when a ring of contraction moves down the wall of the tube. D. Innervation of the Tube 1. Branches of the sympathetic and parasympathetic nervous system innervate the alimentary canal. 2. The innervation of the alimentary canal maintains muscular tone and regulates strength, rate, and velocity of muscular contractions. 3. The submucosal plexus is important for controlling secretions by the gastrointestinal tract. 4.
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ch17_answer_key - Shier, Butler, and Lewis: Holes Human...

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