TEETH– BASIC IDEA ABOUT STRUCTURE AND FUNCTION
|INTRODUCTION:- Teeth are the hardest non- bony structure in the vertebrate body,
attached to the jaw bones. In our body, they are used in biting, chewing and
grinding of the food or in catching of prey. In human teeth are responsible for taking food also.
TYPES OF TEETH:– Most animals have Teeth in their jaws. Teeth are used to cut and break
the food into smaller parts. The kind, number and arrangement of teeth
in a personal or animal is called. ” dentition “. It is of two types:
a) HOMODONT: All the teeth in the jaws are similar in shape and structure e.g fish and frog.
b)HETERODONT: The teeth in the jaws are not similar in shape and
structure e.g. cows and humans.
Mammals have heterodont dentition since all the teeth are not alike in them.
There are four types of teeth in mammals; incisors, canines, premolars and molars.
The number, size and shape of the teeth are related to the food the animals consume.
STRUCTURE OF A HUMAN TOOTH:–
The human teeth are enclosed in bony sockets or alveoli in the jaw bones.
These are called ” thecodont”. Each tooth consists of three parts.
* ROOTS— The basal part, embedded in the alveoli.
* NECK— They middle part enclosed in the gum.
* CROWN— They visible part projected beyond the gum.
In longitudinal section of a tooth, the following parts are seen:-
a) Enamel: The white shiny outer covering of the crown is called enamel or ivory.
Ø It is the hardest substance in the body. It can withstand tremendous pressure
while eating. Enamel wears away with age and dentine is exposed and the
teeth start looking yellow.
b) Dentine: It is the yellowish bone- like tissue that lies inside the enamel.
Dentine is not hard like enamel but harder and stronger than a bone.
c) Cement: It is a bone like structure that covers and fixes the root of
tooth within the socket of bone.
d) Pulp cavity and pulp: Pulp cavity is the central space in the tooth and is filled with soft
connective tissue. The pulp is richly supplied with blood capillaries, nerve fibres and
lymph vessels. These enter the pulp through root canal. The narrow part of the pulp
cavity is called root canal.
e) Odontoblasts: Dentine contains many canals having dentine producing cells called
f) Periodontal fibres: Many fibres connect cement at one end and the jawbone at the other
end and hold the tooth firmly in position which are known as periodontal fibre.
CHARACTERISTICS OF HUMAN TEETH: The human teeth are;
a) THECODONT—The teeth are fastened in the socket of jaw bones.
b) DIPHYODONT: In human, two sets of teeth are developed during lifetime.
These are known as temporary or deciduous teeth and permanent teeth.
The temporary teeth appear first. They are replaced by permanent set of teeth.
The deciduous or milk teeth fall because their roots begin to dissolve making way for
permanent teeth. The total number of teeth in adult is 32 which are permanent, but children
up to age of 12 years have just 20 temporary or milk teeth.