Alimentary canal

The alimentary canal is the continuous passage through which food travels from the mouth to the anus. As food moves along it, food is broken down, useful substances are absorbed and undigested material is removed.

Route through the alimentary canal

1. Mouth: Food and drink enter the body. This is called ingestion. Food begins to be broken down in the mouth.
2. Oesophagus: Swallowed food passes down the oesophagus to the stomach.
3. Stomach: The stomach churns the food and continues its digestion.
4. Duodenum: Food enters the duodenum, the first part of the small intestine.
5. Ileum: Food passes along the small intestine to the ileum, where digested nutrients are absorbed into the blood.
6. Colon: The remaining material enters the colon, part of the large intestine, where water is absorbed. Undigested material forms faeces.
7. Rectum and anus: Faeces are stored in the rectum and leave the body through the anus. This removal is called egestion.

The order of these connected organs identifies the route food takes through the canal, including when the organs are shown in a diagram or image.

Absorption and assimilation

Absorption is the movement of nutrients from the intestine into the blood. After absorption, body cells take up and use the nutrients. This use of nutrients by cells is called assimilation.

Associated digestive organs

Associated digestive organs help break down food, but food does not pass through them. Instead, food travels along the alimentary canal, while these organs release substances into it.

The salivary glands lie near the mouth and produce saliva. Saliva enters the mouth, where it moistens food and begins its digestion.

The pancreas lies behind the stomach, close to the duodenum, the first part of the small intestine. It supplies digestive substances, including enzymes, to the duodenum through a duct.

The liver produces bile, which helps the digestion of fats by breaking them into small droplets. The gall bladder, beneath the liver, stores bile and releases it into the duodenum through a duct.

In diagrams and images, the associated organs can be recognised by their positions outside the alimentary canal and their connections to it: the salivary glands release saliva into the mouth, while the pancreas and gall bladder release their substances into the duodenum.