We eat food for energy. But the food that we eat cannot be directly utilised by our body. It has to undergo a process digestion, through which the food substances are broken down into simpler substances, whereby assimilation in the body is possible. Digestion therefore can be defined as a process, starting from ingestion of food, followed by reducing it to simpler substances through chemical or enzymatic action which can be utilized by the various tissues of the body according to their requirements.
Enzymes are chemical substances secreted by the glands of the alimentary tract (including the salivary glands and pancreas), which has the power of acting on a food stuff and converting it to simpler form, by which it can be absorbed. The process of digestion takes place in the digestive system consisting of all organs, which are connected in the chewing, swallowing, digestion and absorption of food and in the elimination of waste products from the body. Alimentary Canal
It consists of the digestive tube or aliment canal and the accessory organs of digestion. The alimentary tract is about 9 meters long tube starting from the mouth and ending at the anus. In consists of-the following parts.
1. The mouth
2. The pharynx
3. The esophagus
4. The stomach
5. The small intestine
6. The large intestine
7. The rectum and the anal canal.
The accessory organs of digestion are:
1. The teeth
2. Three pairs of salivary glands
3. The pancreas
4. The liver and the bilary duct.