Breakdown of food into smaller pieces without chemical change to the food molecules. This happens in the mouth and stomach.
Physical digestion
Increases the surface area of food for the action of enzymes in chemical digestion
Role of teeth
They are used for chewing to increase the surface area of the food so that it can be exposed to saliva and other digestive juices and broken down more quickly
Different types of teeth
Incisors - chisel-shaped for biting and cutting
Canines - pointed for tearing, holding and biting
Premolars and molars - larger, flat surfaces with ridges at the edges for chewing and grinding up food
Crown
The part of the tooth visible above the gum
Tooth decay
1. Food is left on the teeth
2. Bacteria use the sugar (glucose) to respire (anaerobically)
3. Bacteria convert the sugars into lactic acid
4. The acid reacts with the enamel
5. The enamel dissolves
6. The softer dentine is exposed
7. If nerves are exposed, pain is felt
Preventing tooth decay
Avoiding foods with a high sugar content
Using toothpaste and drinking water containing fluoride
Regular, effective brushing to prevent the build-up of plaque (a sticky layer on the teeth)
How fluoride reduces tooth decay
Reducing the ability of bacteria on plaque to produce acid
Helping to replace calcium ions and phosphate ions lost by tooth enamel because of acid attack
