Page 17 - Science Class 07

Mouth fall out due to some dental disease or accident.
The mouth is the beginning of the diges ve
tract; and in fact, diges on starts here when
taking the first bite of food. Chewing breaks the
food into pieces that are more easily digested,
while saliva mixes with food to begin the
process of breaking it down into a form that
your body can absorb and use.
Mouth
Teeth
There are two sets of teeth in our mouth or
oral cavity. Each tooth is rooted in separate
socket in the gums. Teeth grow in accordance
with the age. When a child is born it has no
teeth. But a fully grown person has thirty two
teeth. We can categorise teeth in milk teeth
and permanent teeth.
Milk Teeth
A newly born baby has no teeth. Teeth start
growing at the age of about eight months.
When a baby grows two years old it has about
twenty teeth, ten in upper jaw and ten in the
lower jaw. These teeth are called milk teeth as
these teeth start falling a er a few years. These
teeth are gradually replaced by permanent
teeth.
Permanent Teeth
Permanent teeth grow a er falling out of the
milk teeth. These are thirty two in numbers.
These teeth do not fall out naturally. They may
Science-7
Once a permanent tooth falls it will not be
replaced naturally.
Types of Teeth
On the basis of shape, structure and func on,
we can also group the teeth of human beings.
Teeth can be grouped into the following types:
v Incisors – The four front teeth in both the
upper and lower jaws are called incisors.
Their primary func on is to cut food.
Incisors have a single root and a sharp
incisal edge.
v Canines – There are four canines in the oral
cavity. Their main func on is to tear food.
They have the single longest root of any
tooth. They also serve to form the corners
of the mouth.
v Premolars (Bicuspids) – These teeth are
located behind and adjacent to the canines
and are designed to crush food.
v Molars – The most posterior teeth in the
mouth are the molars. They have broader
and fla er surfaces with 4-5 cusps. They
are designed to grind food.
Canine
Molars
Premolars
Incisors
Incisors Canine Premolars Molars
Different types of teeth present
in human mouth cavity.
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