Transcript Human Body

Digestion
Chapter 3, Lesson 3 and 4
Brain Pop
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Digestion
Three Functions – p. 81
1.
Digestion
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Your body breaks down food into small nutrient
molecules
Three Functions – p. 81
2 types
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Mechanical – bits of food are torn or ground into
smaller pieces
Chemical – chemicals (enzymes) break down foods
into nutrients
Functions (cont.)
2.
Absorption
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Nutrient molecules pass through the walls of the
digestive system into the blood
Most absorption happens in the small intestines
Functions (cont.)
3. Elimination
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The large intestine eliminates materials that are
not absorbed
Think Time
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Compare the digestive system to sink and
garbage disposal work.
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Digestion:
Absorption:
Elimination:
The Mouth, Esophagus, and
the Stomach – p. 82
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Organs where mechanical digestion is completed
and chemical digestion begins
Mouth
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Once you bite off a piece of food, mechanical and
chemical digestion begins
Mechanical Digestion
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Teeth cut, tear, crush and grind food
Tongue pushes food toward your teeth
Chemical Digestion
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Saliva contains chemicals and moistens food
Think Time
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Complete the Diagram on Page 82
Roles (cont.)
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Esophagus – p. 84
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Muscular tube connecting the mouth to the stomach
As you swallow, epiglottis seals off windpipe and
prevents food from entering in the lungs
Food moves into esophagus after swallowing
Lined with mucus to make food move easily
Involuntary muscle contractions (peristalsis) pushes
food toward stomach
Roles (cont.)
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Stomach p. 84
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When food leaves the esophagus it enters the
stomach
Most mechanical and some chemical digestion
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Mechanical – smooth muscle contracts to produce
churning motion; mixes the food with fluids
Chemical – the churning food mixes with digestive
juices (pepsin, hydrochloric acid)
Food stays in stomach a few hours until
mechanical digestion is complete
Think Time
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Complete the Sequence and Infer on page 84
The Small Intestine – p. 87
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6 meters long and makes up two-thirds the
length of the digestive system
Only 2 to 3 centimeters in diameter
Most of the chemical digestion and
absorption of nutrients take place here
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Villi (finger-shaped structures) help increase the
surface area
Nutrients pass from cell on the surface of villi into
blood vessels to be delivered to body cells
Think Time
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Complete the Diagram on Page 87
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In Detail Box 1 Describe the role of the Small
Intestine in Digestion
In Detail Box 2 Describe the role of the Small
Intestine in Absorption
In Detail Box 3 Predict the role of the Small
Intestine in Elimination
Liver and Gall Bladder – p. 88
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Liver produces bile to break up fat particles
The gall bladder stores the bile once it is
made
Bile is released when food enters the small
intestine but does not aid in chemical
digestion (breaks large fat particles into
smaller ones)
Pancreas – p. 88
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Located between the stomach and first part
of the small intestine
Produces digestive enzymes to break down
carbohydrates, proteins and fats
Enzymes are sent to small intestine to help
with chemical digestion
Think Time
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Complete the Diagram on Page 88
Large Intestine – p. 90
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Most nutrients have been absorbed by the
end of the small intestine
Water and undigested food moves from the
small to large intestine (last section of the
digestive system)
As material moves through the large
intestine, water is absorbed into blood stream
and rest is prepared for elimination
About 1.5 meters long
Large Intestine
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Contains bacteria to make certain vitamins
from feeding on materials as they pass
through
Large intestine ends in a short tube called the
rectum
Waste material is eliminated through the
anus
Think Time
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Complete the Diagram on Page 91