Chapter 3 Digestion: From Meals to Molecules

From Atoms to Organisms Copyright 2010, John Wiley & Sons, Inc. 2

Major Organ Systems of the Body Copyright 2010, John Wiley & Sons, Inc. 3

Major Organ Systems of the Body Copyright 2010, John Wiley & Sons, Inc. 4

Major Organ Systems of the Body Copyright 2010, John Wiley & Sons, Inc. 5

Major Organ Systems of the Body Copyright 2010, John Wiley & Sons, Inc. 6

Digestion and Absorption Biochemically, “you are what you eat” is scientifically true! Food and fluid taken into the body is broken down into smaller components so it can be used by the body. Copyright 2010, John Wiley & Sons, Inc. 7

Copyright 2010, John Wiley & Sons, Inc. The Digestive System Copyright 2010, John Wiley & Sons, Inc. 8

Overview of the Digestive System Digestion: process of breaking food into components small enough to be absorbed by the body Absorption: process of taking substances into the interior of the body Gastrointestinal tract: hollow tube consisting of the mouth, pharynx, esophagus, stomach, small intestine, large intestine and anus Transit time: amount of time it takes food to pass the length of the GI tract Feces: body waste, including unabsorbed food residue, bacteria and dead cells Copyright 2010, John Wiley & Sons, Inc. 9

Copyright 2010, John Wiley & Sons, Inc. Digestive Secretions Digestion inside the GI tract is assisted by digestive secretions. Mucus: viscous material produced by goblet cells; mucus moistens, lubricates and protects the GI tract Enzymes: protein molecules that speed up chemical reactions; enzymes are not changed during reactions Copyright 2010, John Wiley & Sons, Inc. 10

Swallowing and Choking Copyright 2010, John Wiley & Sons, Inc. 11

Swallowing and Choking Copyright 2010, John Wiley & Sons, Inc. 12

Moving Food Through the GI Tract Copyright 2010, John Wiley & Sons, Inc. 13

Stomach Structure and Function Copyright 2010, John Wiley & Sons, Inc. 14

Regulation of Stomach Activity Gastric Juice: Mucus Hydrochloric acid Pepsin – Inactive form of protein- digesting enzyme Water Copyright 2010, John Wiley & Sons, Inc. 15

Structure of the Small Intestine Microvilli: Brush Border Copyright 2010, John Wiley & Sons, Inc. 16

Digestion in the Small Intestine Copyright 2010, John Wiley & Sons, Inc. 17

Immune Function in the Small Intestine Phagocyte: Engulf and destroy antigen Lymphocyte: Directly kill invaders or secrete antibodies which destroy antigen Immune system tissues embedded throughtout the Mucosa of small intestine Copyright 2010, John Wiley & Sons, Inc. 18

Absorption: Simple Diffusion, Osmosis, and Activated Transport Active Transport: Requires energy and carrier molecule to transport molecules from lower to higher concentration Facilitated Diffusion: Passive diffusion that requires a carrier molecule to transport solute from higher to lower solute concentration Simple Diffusion: Movement of solute from higher to lower concentration Osmosis: Movement of solvent from lower solute to higher solute concentration 19

Copyright 2010, John Wiley & Sons, Inc. Bacteria on the Menu Scientists recognize that yogurt contains beneficial bacteria, including Lactobacillus and Bifidobacterium. When these living microorganisms are consumed in adequate amounts, they live temporarily in the colon where they inhibit the growth of harmful bacteria and confer other health benefits on the host. However, the bacteria must be consumed frequently because they are flushed out in the feces. Copyright 2010, John Wiley & Sons, Inc. 20

The GI Tract and Immune Function The GI tract plays an important role in protecting the body from infection. The GI tract limits the absorption of toxins and disease-causing organisms. Some cells of the immune system are present in the GI tract: Phagocytes Lymphocytes Antibodies Copyright 2010, John Wiley & Sons, Inc. Copyright 2010, John Wiley & Sons, Inc. 21

Copyright 2010, John Wiley & Sons, Inc. Digestive Disorders Tooth loss affects in chewing food and reduces Nutrient absorption Heartburn, gastro-esophageal reflex disease, Peptic ulcer: when mucosa is destroyed Copyright 2010, John Wiley & Sons, Inc. 22

Copyright 2010, John Wiley & Sons, Inc. Digestive Disorders Constipation Gallstone Deposits of cholesterol, bile pigments and calcium Due to low in fiber and fluids Copyright 2010, John Wiley & Sons, Inc. 23

Eating for Digestive Health Reduce your risk of adverse reactions Read food labels to avoid foods that you are allergic to. Chew each bite thoroughly to maximize digestion and avoid choking. Don’t talk with food in your mouth. Learn the Heimlich maneuver: You could save a life. Reduce the chances of heartburn Eat enough to satisfy your hunger but not so much that you are stuffed. Wait 10 minutes between your first and second courses to see how full you feel. Stay upright after you eat—don’t flop on the couch in front of the television. Avoid constipation by consuming enough fiber and fluid Choose whole-grain cereals such as oatmeal or raisin bran. Double your servings of vegetables at dinner. Eat two pieces of fruit with your lunch. Choose whole-grain bread. Have one or two beverages with or before each meal. Copyright 2010, John Wiley & Sons, Inc. Copyright 2010, John Wiley & Sons, Inc. 24

Copyright 2010, John Wiley & Sons, Inc. Delivering Nutrients Blood Circulation Copyright 2010, John Wiley & Sons, Inc. 25

Copyright 2010, John Wiley & Sons, Inc. Metabolizing Energy Metabolic pathways are series of reactions needed to modify food into a final product that can be used by the body. Catabolic pathways release energy trapped in chemical bonds. Energy from catabolic reactions is converted into ATP. ATP is the energy currency of the cell. Copyright 2010, John Wiley & Sons, Inc. 26

Copyright 2010, John Wiley & Sons, Inc. Eliminating Wastes Copyright 2010, John Wiley & Sons, Inc. 27

Alternate Feeding Methods If an individual cannot take adequate food or fluid by mouth: Enteral or tube feeding TPN: Total Parenteral Nutrition Copyright 2010, John Wiley & Sons, Inc. 28

Copyright 2010, John Wiley & Sons, Inc. End of Chapter 3 Copyright 2010 John Wiley & Sons, Inc. All rights reserved. Reproduction or translation of this work beyond that permitted in section 117 of the 1976 United States Copyright Act without express permission of the copyright owner is unlawful. Request for further information should be addressed to the Permissions Department, John Wiley & Sons, Inc. The purchaser may make back-up copies for his/her own use only and not for distribution or resale. The Publisher assumes no responsibility for errors, omissions, or damages caused by the use of these programs or from the use of the information herein. . Copyright 2010, John Wiley & Sons, Inc. 29