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OPEN DAY
Chapter 3
Digestion, Absorption and
Metabolism
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Learning Objectives
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• Atoms to organisms
• Digestive system
• Digestion and absorption
• Metabolism of Nutrients
Copyright 2011, John Wiley & Sons, Inc.
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You are what you eat!!!
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Digestion and Absorption
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• Biochemically, “you are what you eat” is
true!
• Food and fluid taken into the body is
broken down into smaller components so
it provides all of the energy we need to
stay alive and active.
Copyright 2010, John Wiley &
Sons, Inc.
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Our
Complex Bodies Are Built
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from Simpler Units
• We are all made of atoms, which are the
smallest units of an element that still
retain the properties of that elements
• Atoms can be linked by chemical
bonds to form molecules
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Our
Complex Bodies Are Built
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from Simpler Units
• Organic molecules?
• Carbohydrates, lipids, proteins, and
vitamins
• Inorganic molecules?
• Water and minerals
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Cells
form tissues, tissues form
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organs, organs form organ
systems
• In any living systems, molecules are
organized into cells
• Cells that are similar in structure and
function form tissues
• Tissues are organic in varying
combination into organs.
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Digestion and Absorption
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Copyright 2010, John Wiley &
Sons, Inc.
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Organ
Systems
of
the
Body(p.79)
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Copyright 2010, John Wiley &
Sons, Inc.
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Organ
Systems
of
the
Body(p.79)
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Copyright 2010, John Wiley &
Sons, Inc.
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Digestive system
• Primarily responsible for the movement of
nutrients into the body
• Endocrine, nervous ,urinary, respiratory,
and integumentary systems all help the
nutrients digest and absorb in our body.
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An
of the Digestive
OPENOverview
DAY
System
• The digestive system provides two
major functions: digestion and
absorption
– Digestion is the process of breaking food
into components small enough to be
absorbed into the body
– Absorption is the process of taking
substances into the interior of the body
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An
of the Digestive
OPEN Overview
DAY
System
• Carbohydrate---glucose
• Protein---amino acids
• fat ---fatty acids
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Structure
of the Gastrointestinal
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Tract
• Gastrointestinal tract/GI/gut/digestive
tract/intestinal tract/alimentary canal
• Include the mouth, pharynx,
esophagus, stomach, small and large
intestine, and anus.
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Overview of the Digestive System(p.81)
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Copyright 2010, John Wiley &
Sons, Inc.
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Question
that make you think
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Food Must Be Digested for
Nutrients to be Absorbed
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•Digestive activity begins with the sights,
sounds, and smells of food
•The nervous system signals the
digestive system to ready itself for a
meal.
•Mouth---moist
•Stomach—secrete digestive substances
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Digestion and Absorption
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• The mouth is the entry point for food into
the digestive tract.
• Saliva contains salivary amylase, which helps to
break down carbohydrates and lysozymes, which
help to inhibit bacterial growth in the mouth.
• Chewing mechanically breaks food down,
increasing the surface area in contact with
digestive enzymes.
• Breaks apart fiber that traps nutrients in some
foods.
Copyright 2010, John Wiley & Sons, Inc.
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OPEN DAY
Roles of Saliva
• It moistens the food so that it an easily be
tasted and swallowed.
• It begins the enzymatic digestion of starch.
• It cleanses the mouth and protects teeth
from decay.
• It lubricates the upper GI tract.
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Digestion and Absorption
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• Pharynx and Epiglottis
Copyright 2010, John Wiley & Sons, Inc.
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Digestion and Absorption
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• Esophagus
Copyright 2010, John Wiley &
Sons, Inc.
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Digestion
and
Absorption
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• The brain is
involved in
digestion and
absorption.
Copyright 2010, John Wiley &
Sons, Inc.
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Question that make you think
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Vegetable
and Grain’s Digestion
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time
• Zucchini, broccoli, cauliflower, string
beans, yellow squash, corn on cob - all 45
min. digestion time
• Concentrated Carbohydrates - Grains
90 min. digestion time
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Animal
OPEN DAY proteins ‘s Digestion time
• Egg yolk - 30 min. digestion time
• Whole egg - 45 min.
• Fish - cod, scrod, flounder, sole seafood - 30
min. digestion time
• Fish - salmon, salmon trout, herring, (more fatty
fish) - 45 min. to 60 digestion time
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Animal
OPEN DAY proteins ‘s Digestion time
• Chicken – 1.5 to 2 hours digestion time
(without skin)
• Turkey - 2 to 2 1/4 hours digestion time
(without skin)
• Beef, lamb - 3 to 4 hours digestion time
• Pork – 4.5to 5 hours digestion time
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Questions that make you
think….
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• What is the capacity of the stomach?
• Empty:50ml, male:1400-2400ml，
female:1200-2000ml
• What is chyme?
• Bolus mixed with highly acidic stomach
secretions to from a semiliquid food mass
• How long will the chyme normally store in
the stomach?
• 2-6hours
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Stomach
• Water, alcohol and a few drugs absorbed
in stomach.
• Hydrochloric acid kills most bacteria
present in food, stops the function of
salivary amylase.
• 3 layers of muscle. A Thick mucus layer
protect the wall of stomach.
• Pepsin: protein digesting enzyme.
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Small intestinal
• Pancreas secrets pancreatic juice, which
contains bicarbonate ions and digestive
enzymes to digest carbohydrate, fats and
protein.
• Bile which produced in liver and stored in
gallbladder for fat digestion and
absorption.
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How
the small intestine’s structure help
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absorption of nutrients?
• 20 feet in length
• Intestinal walls are arranged in large
circular folds, increase the surface area in
contact with nutrients
• Inner surface covered with villi
• Ville covered with tiny microvilli to increase
the surface area about size of tennis court.
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Questions that make you
think….
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•What is the length of the small intestinal? 7
meters
•Where does most digestion and absorption
occur? Small intestine
•How long will the chyme normally stay in
the small intestinal? 3-5
•How long will water, nutrients, and fecal
matter normally stay in large intestinal? 1224hours
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Metabolic Reactions
Synthesize and Break Down
Molecules
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• Our bodies use nutrients to produce
energy and to manufacture substances
needed by the body to grow and
maintain itself
• The sum of these chemical reactions is
called metabolism
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Metabolism of Nutrients
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• Metabolic pathways are a series of
reactions needed to transform 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.
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Metabolic Pathways
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• Use energy from ATP to build body
compounds are referred to as anabolic
pathways.
• The anabolic and catabolic pathways of
metabolism occur in the body continually
and simultaneously(p.106)
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Elimination
of Metabolic Wastes
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• Substances that cannot be absorbed by
the body, such as fiber, carbon dioxide,
nitrogen and water must also be removed
from the body.
• What are the ways to eliminate metabolic
waste products?
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Elimination
OPEN DAY
of
Metabolic
Wastes:
Body Organ
System
Copyright 2010, John Wiley &
Sons, Inc.
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Waste Products Must Be
Eliminated from the Body
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• The waste products of metabolism are
eliminated by the lungs, the skin, and the
kidneys
• At the lungs, red blood cells release the
carbon dioxide, which is then exhaled
into the environment
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Waste Products Must Be
Eliminated from the Body
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• A significant amount of water is also lost
from the lungs, by evaporation
• Some water, minerals, and byproducts
breakdown are lost through the skin
perspiration or sweat. But the kidney is the
primary site for the excretion of water and
the nitrogen-containing byproducts of
protein breakdown
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After
OPEN DAYcompleting this chapter,
the student should be able to:
• Name organs that involved in the
gastrointestinal track
• Where does most digestion and absorption
occur?
• What products of digestion are transported
by the lymphatic system
• List 4 ways that waste products are
eliminated from the body
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