Feeding, Digestion and Dentition in Mammals

The solid food most animals eat is usually large, and must first be broken down into small molecules in the alimentary canal before it can be absorbed in the blood stream. This is usually done mechanically and chemically in mammals. 




In mechanical digestion, the teeth break up big chunks of food into small pieces so that they can be swallowed. Food is also mechanically broken down when the action of action of the muscular walls of the alimentary canal churns it around. Food, when broken into small pieces, has a larger surface area, which is essential for effective chemical digestion. 

Chemical digestion is carried out by enzymes.


DENTITION IN MAMMALS

Dentition can be defined as the number of and kinds of teeth present in mammals and their arrangement in the lower and upper jawbones. It is related to the type of teeth a mammal eats.

Types of Dentition
Dentition is of two types:

1. Homodont dentition
2. Heterodont dentition

1. Homodont dentition: Homodont dentition is the type of dentition in which the organisms have the same types of teeth. No set of teeth is specialized for any function. All the teeth are of the same shape, size and functions. Examples of homodont dentition are found in fishes, amphibians and reptiles.

2. Heterodont dentition: Heterodont dentition is the type of dentition in which the organisms possess teeth of different shapes, sizes and functions. Examples of organisms having heterodont dentition are mammals, e.g, rabbits, man, dog, cattle, etc. The mammals generally have four different types of teeth:

• incisors
• canines
• premolars
• molars

Human beings have two sets of teeth: 

• milk teeth and 
• permanent teeth

Milk teeth: This is the first set of teeth, which grow in children after birth. They usually grow when the child is a few months old and ready to feed on solid food. It lasts only for a short time. They do not have molar. They are made up of the incisor, canine, and premolar teeth. They may number up to twenty(20) and later fall off to be replaced by the permanent teeth.

Permanent teeth: This is the set of teeth which grow in adult human beings. They are usually of four types. These are incisor, canine, premolar, and molar teeth. They remain till old age and may number up to 32 in man.

Types of Teeth

There are four types of teeth in mammals. These are: incisors, canines, premolars, and molars.

1. Incisors: These are located int he front of the jaw. They are flat, chisel-shaped with a sharp edge used for cutting and holding on to the prey so that they do not escape.
2. Canines: They are found next to incisors. They are sharp and pointed at the tips. Canines are used for tearing flesh and for catching the prey.
3. Premolars: Premolars are located at the back of the jaw following the canines. They have large, ridged flat surfaces or cusps used for grinding and chewing of food.
4. Molars: Molars are located at the extreme back of the jaws. They are closely packed with rigid surfaces. They are used for chewing and grinding of food.

Structure of a Tooth

All teeth have the same basic structure. A typical tooth is made up of three regions:

1. The crown is the region which projects above the gums
2. The root is the region which lies embedded in the jawbone.
3. The neck is the region of the junction between the crown and the root.

The center of the tooth consists of a pulp cavity. It contains blood vessels and nerves which are extremely sensitive to heat and cold. Enclosing the pulp is a layer of dentine, a hard and bone-like material. The dentine contains some living cytoplasm. A hole at the tip of each root allows the blood vessels and nerves of the pulp to be connected to those of the bones and gums.

Covering the dentine is a white layer, the enamel. Enamel is the hardest material made by animals. It protects the pulp and dentine within.

Enamel is not present in the root region. Instead, a thin layer of cement covers the dentine. The cement is, in turn, surrounded by the peridontal membrane which fixes the tooth to the jawbone. However, the tooth is not fixed rigidly to the jawbone but can move slightly during biting and chewing.

Each tooth has a continuous supply of blood through the hole(s) at the tip of the root. This supply of blood is enough to keep the tooth alive but not enough to allow the tooth to grow. This sort of teeth are known as closed teeth.

Categories: Biology, Digestion, Digestive System