Transcript Lesson 1

Lesson
The Digestive System
1
When does digestion begin?
Digestion begins when you take your
first bite of food.
Food and drink must be changed into
smaller nutrients before they can be
absorbed into the blood and carried
to cells in the body.
Lesson
1
Lesson Objectives
In this lesson, you will learn to:
• Describe the structures and functions of the digestive
system
• Show the pathway of food through the digestive system
Lesson
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Functions of the Digestive System
What Does Your Digestive System Do?
The functions of the digestive system can be divided into three
main processes:
1. Digestion
2. Absorption
3. Elimination
Lesson
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Functions of the Digestive System
The Digestive Processes
• The nervous system triggers the digestive process.
• Digestion includes a mechanical process involving chewing,
mashing, and breaking food into smaller pieces.
• It also includes a chemical process involving digestive juices
that change food into simpler substances.
• After the food has been broken down, nutrients are absorbed
into the blood and delivered to all cells of the body by the
cardiovascular system.
Lesson
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The Digestive System
Functions of the Digestive System
Lesson
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Structures of the Digestive System
Structures Involved in Ingestion
The digestive process begins in the mouth. Ingestion, the first
stage of the digestive process, is the taking of food into the
body.
Structures involved in ingestion include:
• Teeth
• Salivary glands
• Tongue
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Structures of the Digestive System
Teeth
• The primary function of
the teeth is to break the
food you eat into smaller
pieces.
• Mastication prepares
food to be swallowed.
Lesson
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Structures of the Digestive System
Salivary Glands
• The salivary glands in the mouth
produce the first digestive juices
used in the digestive process.
• Saliva produced by these glands
contains an enzyme that begins
to break down the starches and
sugars in food into smaller
particles.
• Saliva also lubricates food,
making it easier to swallow.
Lesson
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Structures of the Digestive System
Tongue
The tongue forms chewed food into a size and shape that can
be swallowed.
• As you swallow, muscular
contractions force food into the
pharynx, or throat.
• The uvula closes the opening to
the nasal passages.
• The epiglottis closes the opening
to the trachea to prevent food
from entering the respiratory
system.
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Structures of the Digestive System
The Esophagus
• When food is swallowed, it
enters the esophagus.
• Food is moved through the
esophagus, stomach, and
intestines by a process called
peristalsis.
• A sphincter muscle at the
entrance to the stomach
allows food to move from the
esophagus into the stomach.
Lesson
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Structures of the Digestive System
The Stomach
The stomach has three tasks in digestion:
1. Mixing foods with gastric juices
2. Storing swallowed food and liquid
3. Moving chyme into the small
intestine
Lesson
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Structures of the Digestive System
The Pancreas, Liver, and Gall Bladder
• In the small intestine, juices
of two other digestive organs
mix with the food to continue
the process of digestion.
• The pancreas produces
enzymes that break down
the carbohydrates, fats, and
proteins in food.
• The liver produces bile,
which is stored in the gall
bladder.
Lesson
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Structures of the Digestive System
The Small Intestine
• The small intestine consists of three parts, the duodenum,
the jejunum, and the ileum.
• As chyme enters the duodenum from the stomach, it is
further dissolved by digestive juices secreted from glands in
the lining of the small intestine, liver, and pancreas.
• Nutrients entering the capillaries that line the villi are
absorbed and carried throughout the body by the
cardiovascular system.
• Unabsorbed material leaves the small intestine in the form
of liquid and fiber and moves by peristalsis into the large
intestine.
Lesson
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Structures of the Digestive System
The Large Intestine
• The undigested parts of food pass into the colon, or large
intestine.
• The main functions of the large intestine are to absorb
water, vitamins, and salts, and to eliminate wastes.
Lesson
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Structures of the Digestive System
Removing Wastes from the Body
• Solid wastes are eliminated
through the large intestine.
• Some waste is excreted
through the pores by
perspiration.
• Carbon dioxide is expelled
through the lungs when you
exhale.
• Liquid wastes are filtered
through the urinary system.
Lesson
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Quick Review
Choose the appropriate option.
Q. The process by which a series of
involuntary muscle contractions
move food through the digestive
tract is called _______.
1. peristalsis
2. mastication
3. digestion
4. absorption
Lesson
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Quick Review - Answer
A. 1. peristalsis
The process by which a series of involuntary muscle
contractions move food through the digestive tract is
called peristalsis.
Click Next to attempt another question.
Lesson
1
Quick Review
Choose the appropriate option.
Q. Which of the following is NOT a
part of the pathway that food
and undigested wastes follow
through the digestive system?
1. Mouth
2. Esophagus
3. Nose
4. Stomach
Lesson
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Quick Review - Answer
A. 3. nose
The pathway that is followed by food and undigested
wastes through the digestive system does NOT include
nose.
Click Next to attempt another question.
Lesson
1
Quick Review
Choose the appropriate option.
Q. The colonic system mechanically
and chemically breaks down
food, absorbs nutrients, and
eliminates wastes.
True
False
Lesson
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Quick Review - Answer
A. False. The digestive system mechanically and chemically
breaks down food, absorbs nutrients, and eliminates
wastes.
Click Next to attempt another question.
Lesson
1
Quick Review
Choose the appropriate option.
Q. The digestive system interacts
True
with the cardiovascular system.
False
Lesson
Quick Review - Answer
1
A. True. The digestive system interacts with the
cardiovascular system.
Click Next to attempt another question.
Lesson
1
End of Lesson 1
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Lesson
1
Functions of the Digestive System
What Does Your Digestive System Do?
The functions of the digestive system can be divided into three
main processes:
1. Digestion
2. Absorption
3. Elimination
Digestion is the
mechanical and
chemical breakdown
of foods for use by the
body’s cells.
Lesson
1
Functions of the Digestive System
What Does Your Digestive System Do?
The functions of the digestive system can be divided into three
main processes:
1. Digestion
2. Absorption
3. Elimination
Absorption is the
passage of digested
food from the
digestive tract into the
cardiovascular system.
Lesson
1
Functions of the Digestive System
What Does Your Digestive System Do?
The functions of the digestive system can be divided into three
main processes:
1. Digestion
2. Absorption
3. Elimination
Elimination is
the expulsion of
undigested food or
body wastes.
Lesson
1
Structures of the Digestive System
Teeth
• The primary function of
the teeth is to break the
food you eat into smaller
pieces.
Mastication
is the process of
• Mastication prepares
chewing.
food to be swallowed.
Lesson
1
Structures of the Digestive System
The Esophagus
• When food is swallowed, it
enters the esophagus.
Peristalsis
• Food is moved through
the is the
which a
esophagus, process
stomach,inand
of involuntary
intestines byseries
a process
called
peristalsis. muscle contractions
move food through the
digestive
• A sphincter muscle
at tract.
the
entrance to the stomach
allows food to move from the
esophagus into the stomach.
Lesson
1
Structures of the Digestive System
The Stomach
The stomach has three tasks in digestion:
1. Mixing foods with gastric juices
2. Storing swallowed food and liquid
Gastric juices are
secretions from the
3. Moving chyme into the small
stomach lining that
intestine
contain hydrochloric
acid and pepsin, an
enzyme that digests
protein.
Lesson
1
Structures of the Digestive System
The Stomach
The stomach has three tasks in digestion:
1. Mixing foods with gastric juices
Chyme
is a
2. Storing swallowed food
and liquid
creamy, fluid
mixture
of food
3. Moving chyme into
the small
and gastric
intestine
juices.
Lesson
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Structures of the Digestive System
The Pancreas, Liver, and Gall Bladder
• In the small intestine, juices
of two other digestive organs
mix with the food to continue
the process of digestion.
Bile is a
• The pancreas produces
yellow-green,
enzymes that break down
bitter fluid
the carbohydrates, fats, and
important in the
proteins in food.
breakdown and
absorption of fats.
• The liver produces bile,
which is stored in the gall
bladder.
Lesson
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Quick Review - Answer
A. Correct! The process by which a series of involuntary
muscle contractions move food through the digestive
tract is called peristalsis.
Click Next to attempt another question.
Lesson
1
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Lesson
1
Quick Review - Answer
A. Correct! The pathway that is followed by food and
undigested wastes through the digestive system does
NOT include the following: nose.
Click Next to attempt another question.
Lesson
1
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Lesson
1
Quick Review - Answer
A. Correct! The digestive system mechanically and
chemically breaks down food, absorbs nutrients, and
eliminates wastes.
Click Next to attempt another question.
Lesson
1
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.
Lesson
Quick Review - Answer
1
A. Correct! The digestive system interacts with the
cardiovascular system.
Click Next to attempt another question.
Lesson
1
Quick Review - Answer
You have answered the question incorrectly. Go back to try
again, or click Next to view the correct answer.