1. Chapter 3 Digestion: From Meals to Molecules

2. From Atoms to Organisms
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3. Major Organ Systems of the Body
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4. Major Organ Systems of the Body
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5. Major Organ Systems of the Body
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6. Major Organ Systems of the Body
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7. 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.
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The Digestive System
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9. 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
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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
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11. Swallowing and Choking
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12. Swallowing and Choking
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13. Moving Food Through the GI Tract
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14. Stomach Structure and Function
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15. Regulation of Stomach Activity
Gastric Juice:
Mucus
Hydrochloric acid
Pepsin – Inactive form of protein-
digesting enzyme
Water
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16. Structure of the Small Intestine
Microvilli:
Brush Border
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17. Digestion in the Small Intestine
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18. 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
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19. 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

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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.
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21. 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
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Digestive Disorders
Tooth loss affects in chewing food and reduces
Nutrient absorption
Heartburn, gastro-esophageal reflex disease,
Peptic ulcer: when mucosa is destroyed
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Digestive Disorders
Constipation
Gallstone
Deposits of cholesterol, bile pigments and
calcium
Due to low in fiber and fluids
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24. 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.
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Delivering Nutrients
Blood Circulation
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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.
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Eliminating Wastes
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28. Alternate Feeding Methods
If an individual cannot take adequate food or fluid by mouth:
Enteral or tube feeding
TPN: Total Parenteral Nutrition
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End of Chapter 3
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