NSG 460_Chapter_03 audio

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Digestion, Absorption, and Metabolism:

Digestion, Absorption, and Metabolism Chapter 3 Copyright © 2012, 2007 Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved.

Role in Wellness:

Role in Wellness Growth, maintenance, and energy needs depends on the nutrients available The digestive system, responsible for processing foods, relies on nutrient intake for its maintenance Processes of digestion, absorption, and metabolism work together to provide all body cells with energy and nutrients.


Digestion Organs of the Digestive Tract Gastrointestinal (GI) tract Digestive system Digestion Processes completed by digestive system Chemical and mechanical digestion

The Mouth:

The Mouth Function of salivary glands Secretes saliva Function of teeth and tongue Formation and movement of bolus

The Esophagus:

The Esophagus A muscular tube through which bolus travels from mouth to stomach Peristalsis Segmentation Cardiac sphincter

The Stomach:

The Stomach Consists of fundus, body, and pylorus Gastric secretions Gastric motility Chyme formation Functions of stomach Pyloric sphincter

The Small Intestine:

The Small Intestine Consists of duodenum, jejunum, and ileum Passage through takes about 5 hours Major organ of digestion and most absorption Villi and microvilli

Hormones and Enzymes:

Hormones and Enzymes Function of hormones Secretions from small intestine, liver, and pancreas include: Secretin Bile Cholecystokinin (CCK) Function of ileocecal valve (sphincter)

The Large Intestine:

The Large Intestine Consists of cecum, colon, and rectum Passage through takes about 9 to 16 hours Site of final absorption of water and some minerals Bacteria in colon produce several vitamins Formation of feces and excretion from colon through anus (sphincter)


Absorption Process by which substances pass through the intestinal mucosa into the blood or lymph Transport processes Passive diffusion and osmosis

Absorption, cont’d:

Absorption, cont’d Facilitated diffusion Energy-dependent active transport Engulfing pinocytosis

Absorption, cont’d:

Absorption, cont’d Determinants of vitamin and mineral absorption Nutrients such as fats, carbohydrates, and protein easily absorbed regardless of level of need Structure of small intestine allows for efficient absorption to occur Villi and microvilli

Absorption, cont’d:

Absorption, cont’d Factors affecting absorption of nutrients Bioavailability Relationship between food and drug absorption Nutrient transport systems General circulatory (blood) system Lymphatic system Liver


Elimination Expulsion of feces or body waste products called defecation Residue may include: Undigested materials such as cellulose and other dietary fibers Undigested fats may combine with dietary minerals such as calcium and magnesium to form residue Additional residue may include water, bacteria, pigments, and mucus

Digestive Process Across Life Span:

Digestive Process Across Life Span Digestive process across the life span Immature GI tract of young infants Allergies Middle years include gallbladder disease and peptic ulcers Age-related lactose intolerance Older years associated with constipation and diverticulosis


Metabolism Set of processes through which absorbed nutrients are used by body for energy and to form and maintain body structures and functions Catabolism Anabolism

Metabolism, cont’d:

Metabolism, cont’d Functions of nutrients Form new cell structures Create new substances such as hormones and enzymes Assist in use of other nutrients in cell Act as catalysts or coenzymes in transforming and using of carbohydrates, proteins, and lipids Provides energy

Metabolism, cont’d:

Metabolism, cont’d Metabolism waste products Excreted through lungs, kidneys, or large intestine Metabolism across the life span Lowered metabolic rates

Overcoming Barriers:

Overcoming Barriers Heartburn Cause Symptoms include burning sensation in esophagus, asthma, chronic cough, and other ear, nose, and throat ailments Gastroesophageal reflux (GER) Preventions and treatment strategies

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Vomiting Reverse peristalsis Purpose Causes loss of fluid and electrolytes Dehydration a concern, particularly for infants

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Intestinal gas Flatus released from lower intestinal tract Formed by bacteria in large intestine due to fermentation, lactose intolerance, constipation, and eating quickly Strategies for decreasing through changes of food-related behaviors

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Constipation Defecation difficult with straining to pass hard, dry stools Caused by slow movement of feces through colon Strategies to decrease include lifestyle behavior changes

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Diarrhea Passing of loose, watery bowel movements Causes: bacterial or viral infections, lactose intolerance, spoiled foods, or even stress Dehydration risk Most at risk are infants and older adults

Toward a Positive Nutrition Lifestyle: Contracting:

Toward a Positive Nutrition Lifestyle: Contracting Contract: a specific agreement with yourself or between you and a friend, spouse, or other relative Agreement represents willingness to attempt to change a health-related behavior Goal or behavior change clearly defined and observable

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