1. Slide 1 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. Chapter 15 The Digestive System

2. Slide 2 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. OVERVIEW OF THE DIGESTIVE SYSTEM (Figure 15-1 and Table 15-1)  Irregular tube called alimentary canal or gastrointestinal (GI) tract and accessory organs of digestion  Food must first be digested, and absorbed

3. Slide 3 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

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5. Slide 5 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. PRIMARY MECHANISMS OF THE DIGESTIVE SYSTEM (Table 15-2)  Ingestioncomplex foods taken into the GI tract  Ingestion — complex foods taken into the GI tract  Digestiongroup of processes that break complex nutrients into simpler ones  Digestion — group of processes that break complex nutrients into simpler ones  Mechanical digestionbreakup of large chunks of food into smaller bits  Mechanical digestion—breakup of large chunks of food into smaller bits  Chemical digestionbreaks large molecules into smaller ones  Chemical digestion—breaks large molecules into smaller ones  Motilitya number of GI movements resulting from muscular contraction  Motility — a number of GI movements resulting from muscular contraction  Secretionrelease of digestive juices and hormones that facilitate digestion  Secretion — release of digestive juices and hormones that facilitate digestion  Absorptionmovement of digested nutrients into the internal environment of the body  Absorption — movement of digested nutrients into the internal environment of the body  Regulationneural, hormonal and other mechanisms that regulate digestive activity  Regulation — neural, hormonal and other mechanisms that regulate digestive activity

6. Slide 6 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

7. Slide 7 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. 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—type varies depending on GI location (tough and stratified or delicate and simple epithelium); mucus production Mucosa—type varies depending on GI location (tough and stratified or delicate and simple epithelium); mucus production Submucosa—connective tissue layer Submucosa—connective tissue layer Muscularis—circular, longitudinal, and oblique (in stomach) layers of muscle important in GI motility Muscularis—circular, longitudinal, and oblique (in stomach) layers of muscle important in GI motility  Peristalsis — “wavelike” movement pushes food down the tract (Figure 15-3)  Segmentation — “back-and-forth” movement (Figure 15-4) 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 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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10. Slide 10 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

11. Slide 11 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. 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 15-5)  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 15-5)  Typical tooth (Figure 15-6) Three main parts—crown, neck, and root Three main parts—crown, neck, and root Enamel, which covers the crown, is hardest tissue in body Enamel, which covers the crown, is hardest tissue in body

12. Slide 12 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

13. Slide 13 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

14. Slide 14 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. MOUTH (cont.)  Types of teeth—incisors, cuspids, bicuspids, and tricuspids  Twenty teeth in deciduous or baby set; average age for cutting first tooth about 6 months; set complete at about 30 months 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 15-5)

15. Slide 15 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SALIVARY GLANDS (Figure 15-7)  Saliva—exocrine gland secretion flows into ducts Serous type—watery and contains enzymes (salivary amylase) but no mucus Serous type—watery and contains enzymes (salivary amylase) but no mucus  Produced by serous-type secretory cells (Figure 15-7, B) Mucus type—thick, slippery and contains mucus but no enzymes Mucus type—thick, slippery and contains mucus but no enzymes  Lubricates food during mastication  Produced by mucus-type secretory cells (Figure 15-7, B)  Parotid glands (Figure 15-7) Largest salivary glands Largest salivary glands Produces serous type saliva Produces serous type saliva Mumps—infection of parotids Mumps—infection of parotids

16. Slide 16 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

17. Slide 17 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SALIVARY GLANDS (Figure 15-7) (cont.)  Submandibular glands—(Figure 15-7) Mixed gland—produces both serous-type and mucus-type saliva (Figure 15-7, B) Mixed gland—produces both serous-type and mucus-type saliva (Figure 15-7, B) Located below mandibular angle Located below mandibular angle Ducts open on either side of lingual frenulum Ducts open on either side of lingual frenulum  Sublingual glands—(Figure 15-7) Produce only mucus-type saliva Produce only mucus-type saliva Multiple ducts open into floor of mouth Multiple ducts open into floor of mouth

18. Slide 18 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. PHARYNX  Anatomic components: nasopharynx, oropharynx, laryngopharynx (see anatomic description in Chapter 4 and Figure 14-4)  Oropharynx most involved segment in digestive process of swallowing or deglutition Regulation of deglutition movements via motor cortex of cerebrum (voluntary) and “deglutition center” of brainstem (involuntary) Regulation of deglutition movements via motor cortex of cerebrum (voluntary) and “deglutition center” of brainstem (involuntary)

19. Slide 19 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. ESOPHAGUS  Connects pharynx to stomach  Dynamic passageway for food  Food enters stomach by passing through lower esophageal sphincter (LES) or cardiac sphincter

20. Slide 20 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. STOMACH (Figure 15-8)  Size—expands after large meal; about size of large sausage when empty  Food enters stomach through (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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22. Slide 22 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SMALL INTESTINE (Figure 15-9)  Size—about 7 meters (20 feet) long but only 2 cm or so in diameter  Divisions Duodenum Duodenum Jejunum Jejunum Ileum Ileum

23. Slide 23 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

24. Slide 24 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. SMALL INTESTINE (cont.)  Wall—contains smooth muscle fibers that contract to produce peristalsis and segmentation movements  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

25. Slide 25 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. 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 Hepatic—drains bile from liver Cystic—duct by which bile enters and leaves gallbladder 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 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 Location—undersurface of the liver Function—concentrates and stores bile produced in the liver Function—concentrates and stores bile produced in the liver

26. Slide 26 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

27. Slide 27 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. 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 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 Pancreatic islets (of Langerhans)—cells not connected with pancreatic ducts; secrete hormones glucagon and insulin into the blood

28. Slide 28 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. LARGE INTESTINE (Figure 15-12)  Divisions Cecum Cecum Colon—ascending, transverse, descending, and sigmoid Rectum 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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30. Slide 30 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. APPENDIX  Blind tube off cecum  No important digestive functions in humans

31. Slide 31 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. PERITONEUM (Figure 15-14)  Definitions—peritoneum, continuous serous membrane lining abdominal cavity and covering abdominal organs; parietal layer of peritoneum lines abdominal cavity; visceral layer of peritoneum covers abdominal organs; peritoneal space lies between parietal and visceral layers  Extensions—largest are the mesentery and greater omentum Mesentery is extension of parietal peritoneum, which attaches most of small intestine to posterior abdominal wall Mesentery is extension of parietal peritoneum, which attaches most of small intestine to posterior abdominal wall Greater omentum, or “lace apron,” hangs down from lower edge of stomach and transverse colon over intestines Greater omentum, or “lace apron,” hangs down from lower edge of stomach and transverse colon over intestines  X-ray studies of the GI tract—radiopaque contrast medium used to help visualize structures in study images

32. Slide 32 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

33. Slide 33 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. DIGESTION (Table 15-3)  Definition—transforms foods into substances that can be absorbed and used by cells Mechanical digestion—chewing (mastication), swallowing (deglutition), and peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract Mechanical digestion—chewing (mastication), swallowing (deglutition), and peristalsis break food into tiny particles, mix them well with digestive juices, and move them along the digestive tract Chemical digestion—breaks up large food molecules into compounds that have smaller molecules; brought about by digestive enzymes (Figure 15-15) Chemical digestion—breaks up large food molecules into compounds that have smaller molecules; brought about by digestive enzymes (Figure 15-15)  Enzymes and chemical digestion Enzymes are specialized protein molecules that act as catalysts Enzymes are specialized protein molecules that act as catalysts Breakdown process called hydrolysis Breakdown process called hydrolysis

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35. Slide 35 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc.

36. Slide 36 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. DIGESTION (cont.)  Carbohydrate digestion—mainly in small intestine Pancreatic amylase—breaks polysaccharides down to disaccharides Pancreatic amylase—breaks polysaccharides down to disaccharides Intestinal juice enzymes Intestinal juice enzymes  Maltase—changes maltose to glucose  Sucrase—changes sucrose to glucose  Lactase—changes lactose to glucose

37. Slide 37 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. DIGESTION (cont.)  Protein digestion—starts in stomach; completed in small intestine Gastric juice enzyme pepsin partially digests proteins Gastric juice enzyme pepsin partially digests proteins Pancreatic enzyme, trypsin, continues digestion of proteins Pancreatic enzyme, trypsin, continues digestion of proteins Intestinal enzymes, peptidases, complete digestion of partially digested proteins and convert them to amino acids Intestinal enzymes, peptidases, complete digestion of partially digested proteins and convert them to amino acids  Fat digestion Bile contains no enzymes but emulsifies fats (breaks fat droplets into very small droplets) Bile contains no enzymes but emulsifies fats (breaks fat droplets into very small droplets) Pancreatic lipase changes emulsified fats to fatty acids and glycerol in small intestine Pancreatic lipase changes emulsified fats to fatty acids and glycerol in small intestine

38. Slide 38 Mosby items and derived items © 2012 by Mosby, Inc., an affiliate of Elsevier Inc. ABSORPTION  Definition—process by which digested food moves from intestine into blood or lymph  Foods and most water minerals and vitamins are absorbed from small intestine; some water and vitamin K also absorbed from large intestine  Surface area absorption Structural adaptations increase absorptive surface area Structural adaptations increase absorptive surface area Fractal geometry—study of fragmented geometric irregular shapes such as those in lining of intestine Fractal geometry—study of fragmented geometric irregular shapes such as those in lining of intestine