Download 400 - Mahtomedi Middle School

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Chapter 15 Section 2 – The Digestive Process Begins – p.516
I. The three functions of the
digestive system:
1. breaks down food into molecules the body can
use
2. molecules absorbed into blood and carried
throughout the body
3. wastes eliminated from body
A. Digestion
Process by which your body breaks down food into
small nutrient molecules
1. Mechanical
Chewing food into small pieces
2. Chemical
Chemicals produced by the body break foods into
their smaller chemical building blocks
Digestion
Digestion
II.
B. Absorption
Nutrient molecules pass through the wall of your
digestive system into your blood
C. Elimination
Materials that are not absorbed, such as fiber, are
eliminated from the body as waste.
The Mouth
A. Mechanical Digestion
in the Mouth
Mechanical and chemical digestion begin in the
mouth
Teeth carry out the first stage of mechanical
digestion
1. Incisors
Center teeth that cut food into bite-sized pieces
2. Canines
Tear and slash food into smaller pieces
3. Premolars &
Crush and grind food
Molars
B. Chemical Digestion in
the Mouth
Begins at the same time as mechanical digestion
1. Saliva


moistens food into a slippery mass
contains enzymes that break down food into
molecules that the body can use
2. Enzymes



proteins that speed up chemical reactions
you produce many types of enzymes
each enzyme has a specific chemical shape
III. The Esophagus
Muscular tube (smooth muscle) that connects mouth
to stomach
A. Epiglottis
Flap of tissue that seals off windpipe while
swallowing to prevent food from entering
B. Mucus
A thick slippery substance that lines esophagus
which makes food easier to swallow
C. Peristalsis
Involuntary muscle contractions that push food from
the esophagus to the stomach, and also occur
throughout the rest of the digestive system
IV. The Stomach
As you eat, your stomach expands to hold all of the
food that you eat
A. Mechanical Digestion
in the Stomach

B. Chemical Digestion in
the Stomach



Three strong layers of smooth muscle contract to
produce a churning motion that mixes food with
fluids
mechanical digestion is complete in the stomach
Digestive juice produced by the stomach contains
hydrochloric acid and pepsin (an enzyme that
breaks down proteins in food)
All solids are broken down into liquids, then
passed to small intestine for final digestion and
absorption