Chapter 3Objectives for Chapter 3What Makes Eating So Enjoyable?PowerPoint PresentationWe Develop a Taste for Certain FoodsSlide 6Aromas and Flavors Enhance the Pleasure of EatingWhat Is Digestion and Why Is It Important?Slide 9Slide 10Slide 11Digestion Is Mechanical and ChemicalPeristalsisDigestion Allows Us to Absorb Nutrients from FoodsSlide 15Slide 16What Are the Organs of the GI Tract and Why Are They Important?From Cells to Organs and Organ SystemsThe EpiglottisThe Stomach Stores, Mixes, and Prepares Food for DigestionSlide 21Anatomy of the StomachThe Stomach Stores, Mixes and Prepares Food for DigestionSurface Area in the Small IntestineMost Digestion and Absorption Occur in the Small IntestineSlide 26Large Intestine Absorbs Water and Some NutrientsSlide 28Anatomy of the Large IntestineEnzymes, Hormones, and Bile Aid DigestionProcess of Digestion and Organs of the GI TractThe Liver, Gallbladder, and Pancreas Are Accessory OrgansSlide 33Slide 34The Accessory OrgansSlide 36What Other Body Systems Affect Your Use of Nutrients?The Circulatory and Lymphatic SystemsThe Excretory SystemWhat Are Some Common Digestive Disorders?Slide 41Slide 42Slide 43© 2012 Pearson Education, Inc.Chapter 3The Basics of Digestion© 2012 Pearson Education, Inc.Nutrition and You, 2eObjectives for Chapter 3Define digestion, absorption, and nutrient transport.Describe the organs involved in digestion and their primary functions.Explain the roles of the gallbladder, liver, and pancreas in digestion.Explain the function of peristalsis and segmentation in the movement of food through the GI tract.Explain the role of enzymes in digestion.List the main carbohydrate-, protein-, and fat-digesting enzymes and the tissues that secrete them.Identify the hormones involved in digestion, including their primary action and their source of origin.Explain the role of the small intestine, villi, and microvilli in digestion.Explain how the circulatory and lymphatic systems transport absorbed nutrients throughout the body.Describe the symptoms and causes of the most common digestive disorders.© 2012 Pearson Education, Inc.Nutrition and You, 2eWhat Makes Eating So Enjoyable?Hunger and thirst: physical needs which drive how much and how often we eatAppetite: another powerful drive, but unreliableInfluenced by food preferences and psychological stimulationMay eat without being hungry or needing nourishment© 2012 Pearson Education, Inc.Nutrition and You, 2eAnimation: Control of Appetite: Hunger and Satiety© 2012 Pearson Education, Inc.Nutrition and You, 2eWe Develop a Taste for Certain FoodsTaste: Five basic categoriesDetected by at least 10,000 taste buds mostly on tongue, but also throat and elsewhere in mouthSweet: tip of tongueSalty: sides of tongueSour: sides of tongueBitter: back of tongue Savory (umami): throughout mouth; not all people are sensitive to this taste sensation© 2012 Pearson Education, Inc.Nutrition and You, 2eWe Develop a Taste for Certain FoodsHumans share an innate preference for sweet (pleasure), salty (electrolytes), and fatty (rich textures and aromas) foods Sometimes food preferences and nutritional needs conflict and make changing food choices challengingBrain recognizes taste: food dissolves in saliva, contacts the tongue surface, taste cells send nerve impulses to brain, translated into taste sensations© 2012 Pearson Education, Inc.Nutrition and You, 2eAromas and Flavors Enhance the Pleasure of EatingBoth mouth and nose contribute to tasting of foodsAromas detected by olfactory cells in nasal cavity as food odors enter both nose and mouth (move to back of throat and into nasal cavity)Flavor refers to both taste and aromaExample: Chocolate tastes sweet but its flavor is “chocolate”© 2012 Pearson Education, Inc.Nutrition and You, 2eWhat Is Digestion and Why Is It Important?Digestion: a multi-step process of breaking down foods into absorbable components using mechanical and chemical means in the gastrointestinal (GI) tract Gastrointestinal tract consists of:MouthEsophagusStomach Small and large intestines Other organs© 2012 Pearson Education, Inc.Nutrition and You, 2eMain roles of the GI tract are to:Break down food into smallest componentsAbsorb nutrientsPrevent microorganism or other harmful compounds in food from entering tissues of the bodyGI tract is about 23 feet long with extensive surface area for nutrient absorptionCells lining GI tract are replaced every three to five daysWhat Is Digestion and Why Is It Important?© 2012 Pearson Education, Inc.Nutrition and You, 2eAnimation: Overview of Digestion and Absorption© 2012 Pearson Education, Inc.Nutrition and You, 2eAnimation: Basic Absorption Mechanisms© 2012 Pearson Education, Inc.Nutrition and You, 2eDigestion Is Mechanical and ChemicalMechanical digestion: chewing, grinding food to aid swallowingPeristalsis: the forward, rhythmic muscular contraction that moves food through GI tractChemical digestion: digestive juices and enzymes break down food into absorbable nutrients© 2012 Pearson Education, Inc.Nutrition and You, 2ePeristalsisFigure 3.1© 2012 Pearson Education, Inc.Nutrition and You, 2eDigestion Allows Us to Absorb Nutrients from FoodsAfter digestion, nutrients are absorbed through the walls of the intestines into the body’s two transport systems:Circulatory system (blood)Lymph systemSent to the liver for processing before delivery to the body’s cellsGI tract is highly efficient: 92 to 97 percent of nutrients from food are digested and absorbed© 2012 Pearson Education, Inc.Nutrition and You, 2eDiet Dream Drug: Hope or Hype: Pros and Cons of Alli© 2012 Pearson Education, Inc.Nutrition and You, 2eDiscussion QuestionsWhat does Alli claim to do in the body to help you lose weight?What are some of the unpleasant side effects of using Alli?What is the typical behavior of people using diet drugs?Diet Dream Drug: Hope or Hype: Pros and Cons of Alli© 2012 Pearson Education, Inc.Nutrition and You, 2eWhat Are the Organs of the GI Tract and Why Are They Important?Digestion begins in the mouthSaliva released: contains water, electrolytes, mucus and a few enzymesSoftens, lubricates, dissolves food particlesBolus (food mass) moves into pharynx, is swallowed, and enters the esophagusEpiglottis closes off trachea during swallowing to prevent food from lodging in the windpipe© 2012