Chapter Five: Digestion and
Absorption
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Trace the path followed by food from the
mouth to the anus.
Explain what is meant by peristalsis and the
role of villi and microvilli.
Describe and contrast digestion that takes
place in the mouth, stomach, small intestine,
and colon
Describe the functions of the liver, gall
bladder, and bile as related to digestion
Digestion and Absorption, cntd.
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Name and describe the functions of the
two nutrient transport systems in the
body.
Identify the final products of digestion.
Identify life style factors that affect
digestion and absorption.
Identify common digestive problems.
Anatomy of the Digestive Tract
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Mouth: Provides enzyme—salivary amylase—
begins starch digestion
Bolus: term given to swallowed food
Esophagus: Pathway from mouth to
stomach—separated from stomach by cardiac
sphincter muscle
Stomach: Starch digestion ceases; beginning
of digestion of fats & protein by gastric
juices; Vit. B12 activated by intrinsic factor;
Iron may more absorbable by acidic medium;
food mass now referred to as Chyme
Anatomy of Dig. Tract contd.
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Pylorus: sphincter muscle between stomach
and small intestine
Small Intestine: Enzymes from gall bladder,
pancreas plus intestine completes digestion of
Carbohydrates, Fats, & Protein
Bile: emulsifier produced in liver that
emulsifies fat—stored in gall bladder
Large Intestine: Reabsorbs water and some
nutrients
Involuntary Muscles & Glands
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Peristalsis: involuntary muscle action of
digestive tract that moves food mass
along the tract
Glands:
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Exocrine: releases secretions “out” into
the digestive tract, e.g. enzymes
Endocrine: releases secretions “into” the
blood; triggers exocrine glands to secrete
Digestive Process:
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Foods are broken down into basic units of
energy nutrients
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Fat: glycerol and fatty acids
Protein: amino acids
Carbohydrate: monosaccharide—glucose
Body organs that secrete digestive juices:
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Salivary glands in mouth—salivary amylase
Stomach: Gastric juices--HCL
Small Intestine: Digestive enzymes
Digestive Process, cntd.
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Digestion:
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Liver and Pancreas: Bile and Digestive enzymes
Starts in the mouth with carbohydrate
Stomach adds HCL acid, water & enzymes
Mucus protects walls of stomach from being
digested
Small intestine: most digestion completed
Colon: Reabsorbs water and mineral salts—iron;
breaks down fiber
Rate of Digestion affected by fat content
Absorptive Systems
Absorptive System
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Anatomy of the Digestive Tract
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Small Intestine:
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Surface composed of multiple folds covered
with fingerlike projections called Villi
Each Villi is covered with hairlike projections
projections called Microvilli
Surface of small intestine increased in
order to better absorb nutrients
Absorptive System
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Circulatory System
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Vascular System:
Transports water soluble nutrients
(Carbs, Protein, Water soluble vitamins
and small fat molecules)
 Closed system with a pump
 Contains Red Blood Cells (RBC)
 Nutrients are absorbed through the walls
of the small intestine
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Absorptive System, cntd.
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Lymphatic System
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Transports Fat soluble nutrients (large fat
molecules and fat soluble vitamins)
Open system—no pump
No RBC—Lymph is a watery substance
Molecules collect in duct behind the heart
Enters blood stream through Subclavian Vein
Lipid Transport in Vascular System
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Lipoproteins—fats bundles with protein
HDL and LDL associated with heart disease risk
Systems at their best
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Life style factors can affect digestive
and absorptive systems
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Sleep
Exercise—voluntary and involuntary
muscles affected
State of Mind—stress
Nutrition
Digestive Problems
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Vomiting—reverse peristalsis
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Adaptive mechanism to rid body of irritants
Treat with rest and clear fluids
Diarrhea: movement of digested
particles too rapidly through tract
Constipation: difficulty or pain in
eliminating feces
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Increase fiber or fluids
Natural laxatives—bran, prune juice, fruits
Laxatives—only on physician’s
recommendation