Transcript Fundamentals of Nutrition - Delmar

Section 1
Fundamentals of Nutrition
Copyright © 2003 Delmar Learning, a Thomson Learning company
Chapter 3
Digestion, Absorption, and Metabolism
Copyright © 2003 Delmar Learning, a Thomson Learning company
Objectives
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Describe the processes of digestion,
absorption, and metabolism
Name the organs in the digestive
system and describe their functions
Name the enzymes or digestive juices
secreted by each organ and gland in the
digestive system
Calculate your basal metabolic rate
(BMR)
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Digestion
The breakdown of food in the body in
preparation for absorption.
Mechanical digestion: food is broken up
by teeth and moved along GI tract by
peristalsis.
Chemical digestion: carbohydrates,
proteins, and fats are broken down into
nutrients tissues can absorb and use.
Chapter 3
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Digestion
Chemical changes occur through
hydrolysis (the addition of water and
breaking down of food molecules).
Enzymes act on food substances, causing
them to break down into simple
compounds.
An enzyme can act as a catalyst, which
speeds up the chemical reactions without
itself being changed in the process.
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Absorption
The passage of nutrients into the blood or
lymphatic system.
Nutrients must be in their simplest form
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Carbohydrates: simple sugars
Proteins: amino acids
Fats: fatty acids and glycerol
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Absorption
Most absorption occurs in the small
intestine; some occurs in the large
intestine.
Water is absorbed in the stomach, small
intestine, and large intestine.
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The Digestive System
Chapter 3
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Mouth
Digestion begins here
Enzyme (salivary amylase) acts on starch
Starch is a complex carbohydrate
Teeth break up food; food mixes with
saliva
“Bolus” formed
Length of time food is in mouth is brief
Small amounts of carbohydrates changed
Chapter 3
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Esophagus
Food travels through this muscular tube
Connects mouth to stomach
Peristalsis and gravity act to move bolus
Cardiac sphincter opens at lower end of
esophagus to allow passage of bolus into
stomach
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Stop and Share
What symptom results when the cardiac
sphincter does not close properly?
What is the name of the condition?
What prevents this condition from
occurring?
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Stop and Share
Indigestion or heartburn occurs as a result
of stomach acid flowing back into the
esophagus.
This is called gastroesophageal reflux.
The proper closing of the cardiac sphincter
prevents the acidic content of the stomach
from flowing back into the esophagus.
Chapter 3
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Stomach
Temporary storage of food
Mixing of food with gastric juices
Regulation of a slow, controlled emptying
of food into the intestine
Secretion of the intrinsic factor for vitamin
B12
Destruction of most bacteria inadvertently
consumed
Chapter 3
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Stomach
Hydrochloric acid prepares the gastric area
for enzyme action
Pepsin breaks down proteins
In children, rennin breaks down milk
proteins
Lipase acts on emulsified fats
Chapter 3
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Stop and Share
You are preparing a teaching plan for the
nursing staff working on a GI floor.
You plan to review anatomy and
physiology of the stomach.
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Stop and Share
Complete the following objectives to
prepare for your class:
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Identify the 3 parts of the stomach
Define chyme
Identify the condition that results from
lack of the intrinsic factor in the stomach
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Stop and Share
Fundus: upper portion of the stomach
Body of the stomach: middle area
Pylorus: end of stomach near small
intestines
Chyme: semiliquid mass of food and
gastric juices
Pernicious anemia: lack of intrinsic factor
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Small Intestine
Hormones released
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Secretin causes pancreas to release
sodium bicarbonate to neutralize acidity
of chyme
Cholecystokinin triggers gallbladder to
release bile
Bile
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Emulsifies fat after it is secreted into
small intestine
Produced in liver; stored in gallbladder
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Small Intestine
Enzymes are found in the pancreatic juice
that is secreted into small intestine.
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Pancreatic proteases (trypsin,
chymotrypsin, carboxypeptidases): split
proteins
Pancreatic amylase: converts starches
(polysaccharides) to simple sugars
Pancreatic lipase: reduces fats to fatty
acids and glycerol
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Small Intestine
Produces enzymes
Prepares foods for absorption
Lactase, maltase, sucrase convert lactose,
maltose, sucrose to simple sugars
Peptidases reduce proteins to amino acids
Twenty-two feet long
Villi, hairlike projections, increase surface
area for maximum absorption
Chapter 3
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Small Intestine
Chapter 3
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Stop and Share
A patient with a duodenal ulcer asks you
where the ulcer is located.
How do you respond?
Chapter 3
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Stop and Share
The small intestine is divided into three
sections.
The duodenum is the first section of the
small intestine.
The jejunum is the middle section and the
ileum is the last section.
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Large Intestine
Colon walls secrete mucus to protect
against acidic digestive juices in chyme.
Major tasks of the large intestine:
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Absorb water
Synthesize some B vitamins and vitamin K
Collect food residue
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Stop and Share
You are providing pre-op teaching to a
patient who is going to have intestinal
surgery.
The patient asks you to explain the
structure of the large intestine.
How do you respond?
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Stop and Share
The cecum (blind pocket), colon and
rectum make up the large intestine.
Contents travel through:
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Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
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Large Intestine
Chapter 3
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Metabolism
The use of food by the body after digestion
Results in energy
Occurs after digestion and absorption;
nutrients are carried by the blood to the
cells of the body
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Metabolism
Oxidation
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Nutrients combine with oxygen
Carbohydrates reduce to carbon dioxide
and water
Protein to carbon dioxide, water, and
nitrogen
Also known as aerobic metabolism
Energy is released as nutrients are
oxidized.
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Metabolism
Anaerobic metabolism reduces fats
without the use of oxygen.
The complete oxidation of carbohydrates,
proteins, and fats is commonly called the
Krebs cycle.
Chapter 3
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Metabolism
Anabolism is the process of using energy
from oxidation to create new compounds.
Catabolism is the breakdown of
compounds during metabolism.
Chapter 3
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Metabolism
Controlled primarily by hormones secreted
by the thyroid gland: Triiodothyronine
(T3) and thyroxine (T4).
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Stop and Share
What condition is associated with too
much thyroid hormone?
What condition is associated with too little
thyroid hormone?
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Stop and Share
Hyperthyroidism: metabolism speeds up
and the body metabolizes its food too
quickly, weight is lost.
Hypothyroidism: metabolism slows down
and the body metabolizes its food too
slowly; patient tends to become sluggish
and accumulate fat.
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Energy
Needed for involuntary and voluntary
activity
Involuntary activity: maintenance of body
tissue, temperature, growth
Voluntary activity: walking, swimming,
eating, reading, typing
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Energy
Three groups of nutrients provide energy
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Carbohydrates
Proteins
Fats
Carbohydrates should be primary source of
energy.
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Energy
The unit used to measure the energy value
of foods is the kilocalorie.
kcal: amount of heat needed to raise the
temperature of 1 kilogram of water 1
degree Celsius.
kcal is commonly called calorie.
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Energy
1 gram of carbohydrate yields 4 kcal
1 gram of protein yields 4 kcal
1 gram of fat yields 9 kcal
1 gram of alcohol yields 7 kcal
Chapter 3
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Stop and Share
If you eat a dessert with 19 grams of fat in
it, how many calories from fat does it
have?
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Stop and Share
171 calories
Fat contains 9 kcal per gram
Dessert has 19 grams of fat
9 kcal/gram × 19 grams of fat = 171 kcal
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Basal Metabolic Rate (BMR)
The rate at which energy is needed for
body maintenance.
The energy necessary to carry on all
involuntary vital processes while the body
is at rest.
Also known as resting energy expenditure
(REE).
Chapter 3
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Basal Metabolic Rate (BMR)
Factors that affect BMR: lean body mass,
body size, sex, age, heredity, physical
condition, and climate.
BMR is greater in men than women.
BMR increases during growth and fever.
BMR decreases with age and during
starvation.
Chapter 3
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Calculating BMR
Harris-Benedict equation
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Used by dietitians for persons over age 18
Uses height, weight, and age
Female BMR
655 + (9.6 × weight in kg) + (1.8 × height in cm) –
(4.7 × age)
Male BMR
66 + (13.7 × weight in kg) + (5 × height in cm) –
(6.8 × age)
Chapter 3
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Calculating BMR
Another method used to estimate BMR
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Convert body weight from pounds to
kilograms
Multiply kilograms by 24 (hours per day)
Multiply the answer obtained by 0.9 for a
woman and by 1.0 for a man
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Stop and Share
Calculate the BMR for a woman who
weighs 110 pounds.
Calculate the BMR for a man who weighs
170 pounds.
Chapter 3
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Stop and Share
110 pound woman: BMR 1,080 kcal
110 pounds  2.2 (pounds per kg) = 50 kg
50 kg × 24 hours in a day = 1,200 kcal
1,200 kcal × 0.9 =1,080 kcal
Chapter 3
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Stop and Share
170 pound man: BMR 1,854 kcal
170 pounds  2.2 (pounds per kg) = 77.27 kg
77.27 kg × 24 hours in a day = 1,854 kcal
1,854 kcal × 1.0 =1,854 kcal
Chapter 3
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Conclusion
Food is broken down through the
processes of mechanical and chemical
digestion into nutrients that can be
absorbed.
Enzymes act to break down nutrients.
Absorption occurs mostly in the small
intestines.
Chapter 3
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Conclusion
During metabolism, carbohydrates and
proteins are combined with oxygen in a
process called oxidation.
Energy released during oxidation is
measured by the kcal.
A person’s energy requirement can be
measured in part by estimating the basal
metabolic rate (BMR).
Chapter 3
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