Chapter 3: Digestion and AbsorptionLecture OverviewLearning ObjectivesDigestion (= take apart)Anatomy of the Digestive TractThe Gastrointestinal TractSlide 7PowerPoint PresentationSlide 9Slide 10Muscular Action of DigestionSlide 12Secretions of DigestionSlide 14Slide 15Summary of Digestive Secretions & Their Major ActionsDigestive Fate of SandwichThe Final StageSlide 19AbsorptionAnatomy of the Absorptive SystemSlide 23Slide 24Slide 25Myth of Food CombiningCommon Digestive ProblemsChokingNormal Swallowing and ChokingFirst Aid for ChokingVomitingDiarrheaCeliac DiseaseCeliac Disease DiagnosisSlide 35Celiac Disease InformationConstipationConstipationBelching and GasHeartburn and “Acid Indigestion”UlcersStrategies to Prevent or Alleviate Common GI ProblemsSlide 43Chapter 3: Digestion Chapter 3: Digestion and Absorptionand AbsorptionDr. Alisha RovnerDr. Alisha RovnerUniversity of DelawareUniversity of DelawareNutrition Concepts (NTDT200)Nutrition Concepts (NTDT200)Fall 2013Fall 2013Lecture OverviewDigestion1Absorption2Common Digestive Problems3Learning ObjectivesExplain how foods move through the digestive system Describe the anatomical details of the intestinal cells that facilitate nutrient absorptionDiscuss common GI problems and their treatments.Digestion (= take apart)Digestion (= take apart)Body’s way of breaking down foods into nutrients to prepare for absorptionChallenges of digestionTasks of the mouthDiaphragmSteady movementLubrication of foodDigestive enzyme functionsExcretion of wasteAnatomy of the Digestive TractAnatomy of the Digestive TractGastrointestinal (GI) tractFlexible and muscular tubeMouth → esophagus → stomach → small intestine → large intestine → rectum → anusLumen (inner space within GI tract)•Continuous from one end until the otherThe Gastrointestinal TractThe Gastrointestinal TractAnatomy of the Digestive TractAnatomy of the Digestive TractMouthProcess of digestion begins here•Mastication (process of chewing)When stimulated, taste buds detect 4 basic taste sensations: sweet, sour, bitter, saltySwallowed food passes through pharynxEpiglottis closes off airway so choking doesn’t occur when swallowing After mouth full of food has been chewed and swallowed it’s called a bolusEsophagus (conduit from mouth to stomach)Two sphincters (1 at each end)•Upper esophageal sphincter- opens during swallowing•Lower esophageal sphincter- at the entrance to the stomach, closes behind bolus so doesn’t slip backAnatomy of the Digestive TractAnatomy of the Digestive TractStomachMovement of bolus- retains it for awhile then transfers it to its lower portion Chyme (semiliquid mass)- released through pyloric sphincterPyloric sphincter- opens into small intestines and closes behind chymeAnatomy of the Digestive TractAnatomy of the Digestive TractSmall intestineChyme •Bypasses the opening from bile duct •Travels through three segments of small intestines (duodenum, jejunum and ileum)Large intestine (colon)Remaining contents arrive at ileocecccal valueAs contents pass to the rectum the colon withdraws waterWaste is held until it’s time to get rid of itMuscular Action of DigestionMuscular Action of DigestionSegmentationContraction of circular muscles in small intestine•Mix chyme•Promote contact with absorption cellsSphincter contractionsPeriodically open and closeControl pace of GI tract contentsMuscular Action of DigestionMuscular Action of DigestionPeristalsisCircular and longitudinal muscles working together•Rate and intensity of contractions vary•Factors that may interfere with peristalsisStomach actionCircular, longitudinal, and diagonal musclesTiming the release of chymeSecretions of DigestionSecretions of DigestionBreakdown of food into nutrients requires secretions from 5 organsSalivary glands, stomach, pancreas, liver, small intestineSecretions enter GI tract at various pointsWater Enzymes•Protein facilitator of chemical reactions•HydrolysisSecretions of DigestionSecretions of DigestionSalivaMoisten food for easy passageProtective role for teeth, linings of mouth, esophagus and stomachInitiates carbohydrate digestionGastric juiceActs primarily in protein digestionCells of stomach secrete mucus for protectionpH 2Secretions of DigestionSecretions of DigestionPancreatic juice and intestinal enzymesReleased via ducts into duodenumEnzymes act on all three energy nutrientsSodium bicarbonateBileLiverGallbladderSummary of Digestive Secretions & Their Major ActionsDigestive Fate of SandwichThe Final StageThe Final StageUndigested residuesExercise intestinal musclesRetention of waterColonIntestinal bacteriaRecyclable materials•Water and dissolved saltsAbsorptionAbsorptionSmall intestineMajority of absorption occurs hereTen feet long surface areaAbsorption techniques:•Simple diffusion- cross into intestines freely•Facilitated diffusion- need specific carrier to transport them from one side of cell membrane to another•Active transport- move against a concentration gradient (requires energy)Carrier loads nutrient on outside of cell . . .Carrier loads nutrient on outside of cell . . .Outside cellCell membrane. . . and then releases it on inside of cell.. . . and then releases it on inside of cell.Inside cellFACILITATED DIFFUSIONSome nutrients (such as the water-soluble vitamins) are absorbed by facilitated diffusion. They need a specific carrier to transport them from one side of the cell membrane to the other. (Alternatively, facilitated diffusion may occur when the carrier changes the cell membrane in such a way that the nutrients can pass through.)ACTIVE TRANSPORTSome nutrients (such as glucose and amino acids) must be absorbed actively. These nutrients move against a concentration gradient, which requires energy.Stepped ArtSome nutrients (such as water and small lipids) are absorbed by simple diffusion. They cross into intestinal cells freely.SIMPLE DIFFUSIONFig. 3-9, p. 78Absorption of NutrientsAbsorption of NutrientsAnatomy of the Absorptive SystemAnatomy of the Absorptive SystemVilli Fingerlike projections from folds of small intestinesSelect and regulate nutrients absorbedMicrovilli Hairlike projections on each cell of every villusTraps nutrient participates and transports them into the
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