Chapter 15 The Digestive System

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 2 DIGESTIVE SYSTEM (FIGURE 15-1)  Irregular tube called alimentary canal or gastrointestinal (GI) tract  Food must first be digested, then absorbed, and later metabolized

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 4 WALL OF THE DIGESTIVE TRACT (FIGURE 15-2)  Digestive tract described as tube that extends from mouth to anus  Wall of the digestive tube is formed by four layers of tissue:  Mucosa—mucous epithelium  Submucosa—connective tissue  Muscularis—two layers of smooth muscle  Serosa—serous membrane that covers the outside of abdominal organs; it attaches the digestive tract to the wall of the abdominopelvic cavity by forming folds called mesenteries

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 6 MOUTH  Roof—formed by hard palate (parts of maxillary and palatine bones) and soft palate, an arch-shaped muscle separating mouth from pharynx; uvula, a downward projection of soft palate (Figure 15-4)  Floor—formed by tongue and its muscles; papillae, small elevations on mucosa of tongue; taste buds, found in many papillae; lingual frenulum, fold of mucous membrane that helps anchor tongue to floor of mouth (Figure 15-4)  Typical tooth (Figure 15-5)  Three main parts—crown, neck, and root  Enamel, which covers the crown, is hardest tissue in body

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 10 MOUTH  Types of teeth—incisors, cuspids, bicuspids, and tricuspids  Twenty teeth in temporary set; average age for cutting first tooth about 6 months; set complete at about 2 years of age  Thirty-two teeth in permanent set; 6 years about average age for starting to cut first permanent tooth; set complete usually between ages of 17 and 24 years (Figure 15-6)

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 11 SALIVARY GLANDS (FIGURE 15-7)  Parotid glands—largest salivary glands  Submandibular glands—open into mouth on either side of frenulum  Sublingual glands—open into floor of mouth

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 13 PHARYNX  Subdivided into three anatomical components:  Nasopharynx  Oropharynx  Laryngopharynx

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 14 ESOPHAGUS  Connects pharynx to stomach  Dynamic passageway for food

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 15 STOMACH (Figure 15-8)  Size—expands after large meal; about size of large sausage when empty  Food enters stomach through gastroesophageal (cardiac) sphincter  Pyloric sphincter muscle closes opening between pylorus (lower part of stomach) and duodenum  Wall—many smooth muscle fibers; contractions produce churning movements (peristalsis)  Lining—mucous membrane; many microscopic glands that secrete gastric juice and hydrochloric acid into stomach; mucous membrane lies in folds (rugae) when stomach is empty

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 17 SMALL INTESTINE (FIGURE 15-9)  Size—about 7 meters (20 feet) long but only 2 cm or so in diameter  Divisions  Duodenum  Jejunum  Ileum

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 19 SMALL INTESTINE  Wall—contains smooth muscle fibers that contract to produce peristalsis  Lining—mucous membrane; many microscopic glands (intestinal glands) secrete intestinal juice; villi (microscopic finger-shaped projections from surface of mucosa into intestinal cavity) contain blood and lymph capillaries

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 20 LIVER AND GALLBLADDER  Size and location—liver is largest gland; fills upper right section of abdominal cavity and extends over into left side  Liver secretes bile  Ducts (Figure 15-10)  Hepatic—drains bile from liver  Cystic—duct by which bile enters and leaves gallbladder  Common bile—formed by union of hepatic and cystic ducts; drains bile from hepatic or cystic ducts into duodenum  Gallbladder  Location—undersurface of the liver  Function—concentrates and stores bile produced in the liver

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Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 22 PANCREAS  Exocrine gland that lies behind stomach  Functions  Pancreatic cells secrete pancreatic juice (most important digestive juice) into pancreatic ducts; main duct empties into duodenum  Pancreatic islets (of Langerhans)—cells not connected with pancreatic ducts; secrete hormones glucagon and insulin into the blood

Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc. Slide 23 LARGE INTESTINE (FIGURE 15-12)  Divisions  Cecum  Colon—ascending, transverse, descending, and sigmoid  Rectum  Food enters through ileocecal valve; external opening called anus  Wall—contains smooth muscle fibers that contract to produce churning, peristalsis, and defecation  Lining—mucous membrane

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