Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Processes of the Digestive System  Ingestion –  Propulsion –  Peristalsis –  Segmentation –

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Processes of the Digestive System  Mechanical digestion

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Processes of the Digestive System  Chemical Digestion  Each major food group uses different enzymes  Carbohydrates are broken to  Proteins are broken to  Fats are broken to

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Processes of the Digestive System  Absorption  End products of digestion are absorbed in ___________________________  Food must enter mucosal cells and then into ___________________________________  Defecation

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Control of Digestive Activity  Mostly controlled by reflexes via the _____________ __________________________________________  Chemical and mechanical receptors are located in organ walls that trigger reflexes  Stimuli include:  Reflexes include:  Activation or inhibition of glandular secretions  Smooth muscle activity

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Digestive Activities of the Mouth  Mechanical breakdown  Chemical digestion  Food is mixed with saliva

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Activities of the Pharynx and Esophagus  These organs have no digestive function  Serve as passageways to the stomach

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Deglutition (Swallowing)  Buccal phase  Occurs in the mouth  Food is formed into a bolus  The bolus is forced into the pharynx by the tongue

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Deglutition (Swallowing)  Pharyngeal-esophageal phase  _____________________ transport of the bolus  All passageways except to the stomach are blocked  Peristalsis moves the bolus toward the stomach  The _____________________________________ is opened when food presses against it

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Food Breakdown in the Stomach  Gastric juice is regulated by neural and hormonal factors  Presence of food or falling pH causes the release of  __________________ causes stomach glands to produce protein-digesting enzymes  _______________________________ makes the stomach contents very acidic

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Necessity of an Extremely Acid Environment in the Stomach  Activates ________________________ to ____________________ for protein digestion  Provides a hostile environment for microorganisms

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Digestion and Absorption in the Stomach  Protein digestion enzymes  Pepsin –  Rennin –  The only absorption that occurs in the stomach is of

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Propulsion in the Stomach  Food must first be well mixed  Rippling peristalsis occurs in the lower stomach Figure 14.15

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Propulsion in the Stomach  The pylorus meters out chyme into the small intestine  The stomach empties in _______________ hours Figure 14.15

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Digestion in the Small Intestine  Enzymes from the brush border  Pancreatic enzymes play the major digestive function  Help complete digestion of  Carry out about half of all

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Digestion in the Small Intestine  Pancreatic enzymes play the major digestive function (continued)  Responsible for  Digest nucleic acids  Alkaline content neutralizes acidic chyme

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stimulation of the Release of Pancreatic Juice  Vagus nerve  Local hormones Figure 14.16

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Absorption in the Small Intestine  ____________________is absorbed along the length of the small intestine  End products of digestion  Most substances are absorbed by _________ ________________ through cell membranes  Lipids are absorbed by  Substances are transported to the liver by the hepatic portal vein or lymph

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Propulsion in the Small Intestine  Peristalsis is the major means of moving food  Segmental movements

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Food Breakdown and Absorption in the Large Intestine  No digestive enzymes are produced  Resident bacteria digest remaining nutrients  Produce some  Release  ____________________________________ are absorbed  Remaining materials are eliminated via

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Propulsion in the Large Intestine  Sluggish peristalsis  Mass movements  Presence of feces in the rectum causes a defecation reflex  Internal anal sphincter is relaxed  Defecation occurs with relaxation of the voluntary (external) anal sphincter

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Digestive System  The alimentary canal is a continuous tube by the _______________ week of development  Digestive glands bud from the mucosa of the alimentary tube  The developing fetus receives all nutrients through the placenta  In newborns, feeding must be frequent, peristalsis is inefficient, and vomiting is common

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Digestive System  Teething begins around age  Metabolism decreases with old age  Middle age digestive problems

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Developmental Aspects of the Digestive System  Activity of digestive tract in old age