Teeth & Digestion (Cambridge (CIE) IGCSE Biology): Revision Note

Mechanical digestion is the breakdown of food into smaller pieces without chemical change to the food molecules

It is carried out by the:

• chewing action of teeth

• churning action of the stomach

• emulsification of fats by bile in the duodenum

Teeth are located in the bone of the jaws

They are used for chewing to increase the surface area of the food

• This increases the food's exposure to saliva and digestive enzymes (opens in a new tab) so that it can be broken down more quickly

Different teeth have different shapes, enabling them to perform slightly different functions:

• incisors are chisel-shaped for biting and cutting

• canines are pointed for tearing, holding and biting

• premolars and molars are large, flat surfaces with ridges for chewing and grinding up food

Teeth are embedded in the gums and within the bone of the jaw

The structure of human teeth includes:

• enamel: the hard, outer layer that protects the teeth

• dentine: the layer beneath the enamel that protects the nerves

• pulp: the soft, internal tissue of the tooth that contains nerves and blood vessels

• cement: a hard layer around the root of a tooth that helps to anchor it within the jaw