Digestion Begins in the Mouth
Digestion begins when you bring food into your mouth
(ingestion). The jaw muscles and teeth help you chew
(masticate) your food, as shown in Figure 14.3. Chewing
physically breaks the food into smaller pieces, which in-
creases the surface area of your waffles, sausages, and eggs
that is available for subsequent chemical digestion. Vari-
ous teeth are specialized for the different ways in which
they break apart food (tearing off chunks of sausage, cut-
ting up eggs and waffles, grinding the sausage into bits
that can be swallowed). Salivary glands secrete fluid called
through ducts that lead into the mouth. Saliva mixes
with the food pieces, lubricates and moistens the food,
kills bacteria, and begins to digest starches in your meal.
Movements of your tongue move the food to contact the
teeth and help shape the chewed food into a soft, rounded,
flexible mass called a bolus.
I n g e s t i o n o f f o o d
F ig u r e 1 4 . 3
The mouth receives the food. The mouth is defined by the hard and soft
palates, the tongue, and the cheeks. The teeth and salivary glands are also
associated with the mouth.
V id e o
forms most of the
calcium salts) protects
the tooth from wear
makes up the majority
of the tooth.
pulp (connective tissue
containing nerves and
channel for nerves and
helps anchor the tooth
to the underlying bone.
The three major
are the parotid gland, submandibular
gland, and sublingual gland. They secrete
, which consists
mainly of water (99.5%) and solutes, including:
—Enzyme that begins digestion of starch
—Enzyme that kills bacteria
Sagittal section of a molar
roof of the mouth.
S oft palate
the rest of the
from entering the
tooth sockets and help
to anchor teeth.
forms the floor of the
mouth, manipulates food for
chewing and swallowing,
shapes food, and senses taste.
and grind food.
movement of the tongue