chapter 15 the digestive system
DESCRIPTION
Chapter 15 The Digestive System. DIGESTIVE SYSTEM (FIGURE 15-1). Irregular tube called alimentary canal or gastrointestinal (GI) tract Food must first be digested, then absorbed, and later metabolized. WALL OF THE DIGESTIVE TRACT (FIGURE 15-2). - PowerPoint PPT PresentationTRANSCRIPT
Chapter 15The Digestive System
Copyright © 2005 Mosby, Inc. All rights reserved. 2Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
DIGESTIVE SYSTEM (FIGURE 15-1)
Irregular tube called alimentary canal or gastrointestinal (GI) tract
Food must first be digested, then absorbed, and later metabolized
Slide 2
Copyright © 2005 Mosby, Inc. All rights reserved. 3Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 3
Copyright © 2005 Mosby, Inc. All rights reserved. 4Elsevier items and derived items © 2008, 2004 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—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
Slide 4
Copyright © 2005 Mosby, Inc. All rights reserved. 5Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 5
Copyright © 2005 Mosby, Inc. All rights reserved. 6Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
MOUTHRoof—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
Slide 6
Copyright © 2005 Mosby, Inc. All rights reserved. 7Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 7
Copyright © 2005 Mosby, Inc. All rights reserved. 8Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 8
Copyright © 2005 Mosby, Inc. All rights reserved. 9Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 9
Copyright © 2005 Mosby, Inc. All rights reserved. 10Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 10
Copyright © 2005 Mosby, Inc. All rights reserved. 11Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
MOUTHTypes 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)
Slide 11
Copyright © 2005 Mosby, Inc. All rights reserved. 12Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 12
Copyright © 2005 Mosby, Inc. All rights reserved. 13Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
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
Slide 13
Copyright © 2005 Mosby, Inc. All rights reserved. 14Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 14
Copyright © 2005 Mosby, Inc. All rights reserved. 15Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
PHARYNX
Subdivided into three anatomical components: Nasopharynx Oropharynx Laryngopharynx
Slide 15
Copyright © 2005 Mosby, Inc. All rights reserved. 16Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
ESOPHAGUS
Connects pharynx to stomach
Dynamic passageway for food
Slide 16
Copyright © 2005 Mosby, Inc. All rights reserved. 17Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
STOMACH (Figure 15-8)Size—expands after large meal; about size of large sausage when emptyFood enters stomach through gastroesophageal (cardiac) sphincterPyloric sphincter muscle closes opening between pylorus (lower part of stomach) and duodenumWall—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
Slide 17
Copyright © 2005 Mosby, Inc. All rights reserved. 18Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 18
Copyright © 2005 Mosby, Inc. All rights reserved. 19Elsevier items and derived items © 2008, 2004 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 Jejunum Ileum
Slide 19
Copyright © 2005 Mosby, Inc. All rights reserved. 20Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 20
Copyright © 2005 Mosby, Inc. All rights reserved. 21Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
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
Slide 21
Copyright © 2005 Mosby, Inc. All rights reserved. 22Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
LIVER AND GALLBLADDERSize and location—liver is largest gland; fills upper right section of abdominal cavity and extends over into left sideLiver secretes bileDucts (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
Slide 22
Copyright © 2005 Mosby, Inc. All rights reserved. 23Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 23
Copyright © 2005 Mosby, Inc. All rights reserved. 24Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
PANCREASExocrine 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
Slide 24
Copyright © 2005 Mosby, Inc. All rights reserved. 25Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
LARGE INTESTINE (FIGURE 15-12)Divisions Cecum Colon—ascending, transverse, descending, and sigmoid Rectum
Food enters through ileocecal valve; external opening called anusWall—contains smooth muscle fibers that contract to produce churning, peristalsis, and defecation Lining—mucous membrane
Slide 25
Copyright © 2005 Mosby, Inc. All rights reserved. 26Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 26
Copyright © 2005 Mosby, Inc. All rights reserved. 27Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
APPENDIX
Blind tube off cecum
No important digestive functions in humans
Slide 27
Copyright © 2005 Mosby, Inc. All rights reserved. 28Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
PERITONEUM (FIGURE 15-14)
Definitions—peritoneum, 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 layersExtensions—largest are the mesentery and greater omentum 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 intestinesX-ray studies of the GI tract—radiopaque contrast medium used to help visualize structures in study images
Slide 28
Copyright © 2005 Mosby, Inc. All rights reserved. 29Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 29
Copyright © 2005 Mosby, Inc. All rights reserved. 30Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
DIGESTION (TABLE 15-2)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
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 Breakdown process called hydrolysis
Slide 30
Copyright © 2005 Mosby, Inc. All rights reserved. 31Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
Slide 31
Copyright © 2005 Mosby, Inc. All rights reserved. 32Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
DIGESTION
Carbohydrate digestion—mainly in small intestine Pancreatic amylase—breaks
polysaccharides down to disaccharides Intestinal juice enzymes
Maltase—changes maltose to glucose Sucrase—changes sucrose to glucose Lactase—changes lactose to glucose
Slide 32
Copyright © 2005 Mosby, Inc. All rights reserved. 33Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
DIGESTIONProtein digestion—starts in stomach; completed in small intestine Gastric juice enzyme pepsin partially digests proteins Pancreatic enzyme, trypsin, continues digestion of
proteins 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) Pancreatic lipase changes emulsified fats to fatty acids
and glycerol in small intestine
Slide 33
Copyright © 2005 Mosby, Inc. All rights reserved. 34Elsevier items and derived items © 2008, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.
ABSORPTIONDefinition—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 Fractal geometry—study of fragmented geometric
irregular shapes such as those in lining of intestine
Slide 34