5.
When an individual needs food, he experiences the sensation of
r. This
is controlled by the h
s area of the brain, which receives i
n from
various parts of the body for this purpose.
The process of food selection is related both to previous
g and to
internal
l requirements.
As food enters the oral cavity, bite-size chunks of food are cut off by the upper
and lower
s. These chunks are about the right size for the
to handle.
6.
There are two key facts about digestion:
a. First, digestion is a
l process. Food is broken down into its
constituent parts through the process of
s.
b. Second, this chemical process takes place only at
t surfaces of the food.
7.
Food processes are broken down into smaller and smaller pieces through the
process of
n, or
g. This greatly increases the total s
a____
of the food. The grinding and crushing are accomplished by the p
r and
r
teeth. Keeping the food between the surfaces of the grinding teeth are the
e and
the
s.
8.
The fluids secreted into the oral cavity by the
y glands and the
l
glands are collectively known as
. These fluids serve to
t the surface areas
of the food particles. Saliva also d
s some of the molecules of food items.
These dissolved molecules are tested by the
e
s. Food particles are held
together as a bolus by the m
, which also makes the bolus somewhat slippery.
9.
The bolus is moved posteriorly out of the
h into the p
and
then down through the
s to the stomach. Both the upper and lower air
passageways must be protected as the bolus passes through the
.
10.
The actions of the tongue are produced by its
c muscles and the muscles
of the
bone.
As the bolus approaches the pharynx, the upper air passageway is closed by the
t
e, which also t
s to resist the pressure from the bolus.
MD0007
6-17