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Glencoe Health
Lesson 3
The Digestive
System
LESSON 3
The Digestive System
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Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
BIG
IDEA
The digestive system provides nutrients
and energy for your body through the
digestion of food.
New Vocabulary
mastication
bile
peristalsis
peptic ulcer
gastric juices
appendicitis
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
What Happens During Digestion
Main Idea
In digestion, foods are broken down and
absorbed as nourishment or eliminated as
waste.
The foods you eat must be broken down into
nutrients to be absorbed into the blood and
carried to the body’s cells.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
What Happens During Digestion
Three Main Processes of the Digestive System
Digestion
The mechanical and chemical
breakdown of foods within the stomach
and intestines for use by the body’s cells.
Absorption
The passage of digested food from the
digestive tract into the cardiovascular
system.
Elimination
The body’s expulsion of undigested food
or body wastes.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
How Digestion Works
Main Idea
The digestive system consists of the mouth,
esophagus, stomach, and intestines.
Carbohydrates begin digesting in the mouth,
protein begins digesting in the stomach, and
fats begin digesting in the small intestines.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
How Digestion Works
Digestion includes two processes:
Mechanical
Processes
Chemical
Processes
Chewing, mashing, and breaking food
down.
Secretions produced by digestive organs.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
How Digestion Works
The teeth break the food you eat into smaller
pieces. Mastication prepares food to be
swallowed.
New Vocabulary
mastication
The process of chewing.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
How Digestion Works
Salivary glands
produce saliva,
which contains an
enzyme that begins
to break down the
starches and sugars
in food into smaller
particles.
The tongue
prepares chewed
food for swallowing
by shaping it.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Esophagus
When food is swallowed, it moves through the
esophagus, stomach, and intestines through
peristalsis.
New Vocabulary
peristalsis
A series of involuntary muscle
contractions that moves food through
the digestive tract.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Stomach
The stomach has three tasks:
Mixing foods
with gastric
juices
Storing
partially
digested
food and
liquid
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
Moving food
into the small
intestine
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LESSON 3
The Digestive System
The Stomach
The hydrochloric acid in gastric juices kills
bacteria taken in while food and creates an
acidic environment for pepsin to do its work.
New Vocabulary
gastric juices
Secretions from the stomach lining that
contain hydrochloric acid and pepsin, an
enzyme that digests protein.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Stomach
The stomach holds the food for further digestion
before it is moved into the small intestine.
As food is digested in the stomach, it is
converted to chyme, a creamy, fluid mixture of
food and gastric juices, which is moved into the
small intestine.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Stomach
The three layers of stomach muscles each move in
different directions to aid both mechanical and
chemical digestion.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Pancreas, Liver, and Gallbladder
The liver produces bile and the pancreas
produces other enzymes that break down the
carbohydrates, fats, and proteins in food in the
small intestine.
New Vocabulary
bile
A yellow-green, bitter fluid important in
the breakdown and absorption of fats.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Small and Large Intestines
The small intestine is 20 to 23 feet in length and
one inch in diameter.
It consists of three parts: the duodenum, the
jejunum, and the ileum.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Small and Large Intestines
About 90 percent of all nutrients are absorbed
through the small intestine.
Unabsorbed material leaves the small intestine
in the form of liquid and fiber and moves by
peristalsis into the large intestine.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Small and Large Intestines
The inner wall of the small intestine contains
millions of fingerlike projections called villi that
are lined with capillaries that absorb the
nutrients.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
The Small and Large Intestines
The undigested parts of the food – fiber, or
roughage – pass into the colon, or large
intestine.
Its function is to absorb water, vitamins, and
salts, and to eliminate waste.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Digestive System Problems
Main Idea
Digestive problems range from indigestion to
acute conditions that require immediate medical
attention.
Taking care of your digestive system begins with
the foods you eat and how you eat them.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Digestive System Problems
Tips for Maintaining Digestive Health
Eat a variety of low-fat, high-fiber foods.
Wash your hands before preparing or eating meals.
Eat slowly and chew your food thoroughly.
Drink at least eight 8-ounce glasses of water a day.
Avoid using food as a way of dealing with your emotions.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Functional Problems
Indigestion
Constipation
Heartburn
Discomfort in the abdomen, sometimes
with gas and nausea.
Feces become dry and hard, making
bowel movements difficult.
A burning sensation in the chest that may
rise up to the throat.
Gas
Cramps or an uncomfortable feeling of
fullness in the abdomen.
Nausea
A feeling of discomfort that sometimes
precedes vomiting.
Diarrhea
The frequent passage of watery feces.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Structural Problems
Tooth decay
Gastritis
Gallstones
Lactose
Intolerance
Colitis
Makes it difficult to chew foods
thoroughly.
Inflammation of the mucous membrane
that lines the stomach.
Blockage of the bile duct between the
gallbladder and the small intestine.
Inability to digest lactose, a type of sugar
found in milk and other dairy products.
Inflammation of the large intestine, or
colon.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Structural Problems
Colon
Cancer
Hemorrhoids
Cancer that usually develops in the
lowest part of the colon, near the rectum.
Veins in the rectum and anus that may
become swollen and inflamed.
Crohn’s
Disease
Inflammation of the lining of the digestive
tract.
Cirrhosis
Scarring of the liver tissue caused by
prolonged heavy alcohol use.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Structural Problems
Appendicitis can cause the appendix to burst,
spreading infection throughout the abdomen,
which can lease to death.
New Vocabulary
appendicitis
Inflammation of the appendix.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Structural Problems
Peptic ulcers can be caused by a bacterial
infection or the overuse of aspirin. They can
cause stomach bleeding.
New Vocabulary
Peptic ulcer
A sore in the lining of the digestive tract.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
Structural Problems
Cirrhosis is caused by prolonged heavy alcohol
use. It can lead to liver failure and may cause
death.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
After You Read
Reviewing Facts and Vocabulary
1. What functions of the digestive system
take place in the small intestine?
Digestion and absorption.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
After You Read
Reviewing Facts and Vocabulary
2. Describe the actions that cause food
to move through the digestive tract.
A series of involuntary muscle contractions,
called peristalsis.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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LESSON 3
The Digestive System
After You Read
Reviewing Facts and Vocabulary
3. What are three behaviors that help
prevent indigestion?
Sample answer: Eat less food, eat meals slowly,
and chew food thoroughly.
Glencoe Health Chapter 15 Cardiovascular, Respiratory, and Digestive Systems
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Glencoe Health
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Chapter 15
Cardiovascular,
Respiratory, and
Digestive Systems
Lesson 3
The Digestive System
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