Download Human Biology 2.2

The digestive system2.2
The digestive system breaks down
food.
Nutrients are substances that enable
the body to move, grow, and maintain
homeostasis.
Proteins
Carbohydrates
Fats
Water
Digestion is the process of breaking
down food into useable materials.
food
breaking down
energy
The muscular action of digestion is
called peristalsis.
Digestion
Moving
Wavelike motion
Smooth muscle
Mechanical Digestion
Teeth chew food before
swallowing.
Infants without teeth must
have their food cut up or
mashed.
Physical changes break food into smaller pieces.
The stomach mashes and pounds food during peristalsis.
Chemical
Digestion
Mechanical
Digestion
Food is
Simply
changed
breaks
Digestion
into a
down food
different
into smaller
substance
pieces
Materials are broken down as they
move through the digestive tract.
I. The mouth (A) and the
esophagus (B) are the first
steps in digestion.
A. Both mechanical and chemical
digestion begin in the mouth.
B. The esophagus moves food
between the mouth and the
stomach.
II. The stomach (C) is the
second step in
digestion
A. The stomach breaks
down food with
chemicals and
muscles.
III. After the stomach, food moves
to the small intestine (D).
A. The small intestines break down
nutrients chemically
B. The nutrients are absorbed into
the villi.
IV. After the small intestine, food
moves into the large intestine
(E).
A. The large intestine absorbs water
and some other nutrients.
• Most nutrients are absorbed in the small
intestine.
• The liver produces bile to break down fats.
• The gallbladder stores bile.
• The pancreas lowers the acidity of food from
the stomach and releases chemicals for
digestion.