Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R 23 The Digestive System P A R T A

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Digestive System: Overview  The alimentary canal or gastrointestinal (GI) tract digests and absorbs food  Alimentary canal – mouth, pharynx, esophagus, stomach, small intestine, and large intestine  Accessory digestive organs – teeth, tongue, gallbladder, salivary glands, liver, and pancreas

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 23.1

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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Gastrointestinal Tract Activities  Ingestion – taking food into the digestive tract  Propulsion – swallowing and peristalsis  Peristalsis – waves of contraction and relaxation of muscles in the organ walls  Mechanical digestion – chewing, mixing, and churning food PLAY InterActive Physiology ® : Motility, pages 3-5

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Gastrointestinal Tract Activities  Chemical digestion – catabolic breakdown of food  Absorption – movement of nutrients from the GI tract to the blood or lymph  Defecation – elimination of indigestible solid wastes

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Peritoneum and Peritoneal Cavity  Peritoneum – serous membrane of the abdominal cavity  Visceral – covers external surface of most digestive organs  Parietal – lines the body wall  The peritoneum  Lubricates digestive organs  Allows them to slide across one another

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Salivary Glands  Produce and secrete saliva that:  Cleanses the mouth  Moistens and dissolves food chemicals  Aids in bolus formation  Contains enzyme that breaks down starch (salivary amylase)  Three pairs of glands – parotid, submandibular, and sublingual

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Deglutition (Swallowing) Figure (a) Tongue Trachea Pharynx Epiglottis Glottis Upper esophagea sphincter contracted Bolus of food

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Deglutition (Swallowing) Figure (b) Upper esophageal sphincter relaxed Epiglottis Esophagus Uvula Bolus

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stomach  Chemical breakdown of proteins begins and food is converted to chyme  Main areas include the fundus and the pylorus  Interior lining characterized by rugae

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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Stomach  Epithelial lining is composed of:  Goblet cells that produce a coat of alkaline mucus  Gastric pits contain gastric glands that secrete gastric juice and mucus

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Microscopic Anatomy of the Stomach Figure 23.15a

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Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glands of the Stomach Fundus and Body  Gastric glands of the fundus and body have a variety of secretory cells  Mucous neck cells – secrete mucus  Parietal cells – secrete HCl  Chief cells – produce pepsinogen (converted to its active form pepsin)

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Digestion in the Stomach  The stomach:  Holds ingested food  Degrades this food both physically and chemically  Delivers chyme to the small intestine  Enzymatically digests proteins with pepsin

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Gastric Contractile Activity Figure 23.18