Porth's Essentials of Pathophysiology, 4e

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U N I T

Gastrointestinal and Hepatobiliary Function

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Organization and Function of the Gastrointestinal Tract Upper Gastrointestinal Tract Small Intestine Lower Gastrointestinal Tract Gastrointestinal Wall Structure Mucosa Submucosa Muscularis Externa Serosa and Adventitia Gastrointestinal Innervation and Motility Neural Control of Gastrointestinal Motility Enteric Nervous System Innervation Autonomic Innervation Swallowing and Esophageal Motility Gastric Motility Small Intestinal Motility Colonic Motility and Defecation Secretory Functions of the Gastrointestinal Tract Gastrointestinal Secretions Salivary Secretions Gastric Secretions Intestinal Secretions Gastrointestinal Hormones Digestion and Absorption in the Gastrointestinal Tract Small Intestinal Digestion and Absorption Carbohydrate Digestion and Absorption Protein Digestion and Absorption Fat Digestion and Absorption Colonic Absorption and Intestinal Flora Anorexia, Nausea, and Vomiting Anorexia Nausea and Vomiting

C h a p t e r

Structure and Function of the Gastrointestinal System he gastrointestinal (GI) tract is an amazing struc- ture in which food is dismantled and its nutrients absorbed, wastes are collected and eliminated, and vita- mins synthesized. The GI tract is also becoming increas- ingly recognized as an endocrine organ that produces and augments hormones that contribute to the regula- tion of appetite and food intake and function in the use and storage of nutrients. As a matter of semantics, the GI tract also is referred to as the digestive tract , the alimentary canal , and, at times, the gut. The intestinal portion also may be called the bowel. For the purposes of this text, the liver and pancreas (discussed in Chapter 30), which produce secretions that aid in digestion, are considered accessory organs. T Organization and Function of the Gastrointestinal Tract The major physiologic function of the GI tract is to provide the body with a continual supply of water and other nutrients. It carries out this function through processes involving motility, secretion, digestion, and absorption. In the digestive tract, as food moves slowly along its length it is systematically broken down into ions and molecules that can be absorbed into the blood

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