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Nutrition chapter 3


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Digestion, Absorption, and Metabolism:

Digestion, Absorption, and Metabolism Chapter 3 ATI Ch 2 Copyright © 2012, 2007 Mosby, Inc., an affiliate of Elsevier Inc. All rights reserved. 1

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. 2


Digestion Breakdown of nutrients Organs of the Digestive Tract Mouth to anus Gastrointestinal (GI) tract Digestive system Ingestion, digestion absorption and elimation 3

The Mouth:

The Mouth Function of salivary glands Secretes saliva Function of teeth and tongue Formation and movement of bolus Chemical digestion Mechanical digestion 4

Digestion in the mouth:

Digestion in the mouth Digestion of CHO begin in the mouth Salivary glands secrete saliva >contains water, enzymes(amylase) Break bonds in the chains of starch Enzymes do not affect the fats, proteins, vitamins, minerals and fiber 5

The Esophagus:

The Esophagus A muscular tube through which bolus travels from mouth to stomach Peristalsis Cardiac sphincter 6

The Stomach:

The Stomach Function Consists of fundus, body, and pylorus Gastric secretions Gastric motility Chyme formation Pyloric sphincter 7

Digestion in Stomach:

Digestion in Stomach Initial breakdown of protein occur in stomach Acids in stomach uncoil(denature) the proteins Enzyme pepsin and stomach acid act as catalyst Digestion of some fat by gastric lipase Digestion of sucrose(very small amt ) Protein carrier attaches to vit B12 8

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 9

Pancreas and liver:

Pancreas and liver Pancreas and liver digestive juices to duodenum Pancreatic juice..enzymes act on fats, proteins and CHO Bile secreted by liver…stored in gallbladder..releases when fat present Fat slows digestion Fats, cho , protein, broken down to basic building blocks before absorbed 10

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) 11


Absorption Process by which substances pass through the intestinal mucosa into the blood or lymph Small intestine Release of Absorbed nutrients Transport processes Passive diffusion and osmosis 12

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 13

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 14


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 15

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 16


Metabolism Set of processes through which absorbed nutrients are used by body for energy and to form and maintain body structures and functions Catabolism-breaking down..release energy Anabolism-building up..use of energy\ energy nutrients metabolized to form CO2, H2O,heat and ATP Excess energy stored- Glucose converted to glycogen 17

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 Provides energy 18

Metabolic rate:

Metabolic rate Speed at which food energy is burned BMR- amt of energy used when body is at rest Affected by lean body mass and hormones Men have higher metabolic rate 19

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 20

Overcoming Barriers, cont’d:

Overcoming Barriers, cont’d Vomiting Reverse peristalsis Purpose Causes loss of fluid and electrolytes Dehydration a concern, particularly for infants 21

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 Gradually increase fiber if Increase fluid 22

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 23

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 Encourage fluid replacement 24