There are a number of organs in the body which digest food. They are linked together and form the digestive system. The main feature of the digestive system is a tube which is about seven metres long in an adult. It is made from four organs the gullet, stomach, small intestine and large intestine. Two more organs are connected to this tube. They are the liver and the pancreas.

The digestion of food begins in the mouth. The teeth break up the food into small pieces. The tongue rolls the pieces up into a pellet which is small enough to swallow. Saliva coats the pellet and makes it slippery and easy to swallow. The tongue pushes the pellet of food to the back of the mouth ready for swallowing. When you swallow, more muscles take over in moving the food. They are in the wall of the gullet. This is the tube which connects the mouth to the stomach. The muscles squeeze the tube behind the food then push the food down with a kind of rippling motion. The muscles in the gullet are so strong that they can even push food upwards so a person could eat or drink something standing on their head!

Muscles line the wall of the whole digestive system. The stomach wall has many muscles. The stomach is a muscular bag. The food may stay in it for several hours. During that time the muscles in the stomach wall churn up the food to help break it down. When the food leaves the stomach it is pushed along by muscles in the walls of the intestines.

The digestive system produces a number of liquids which are sometimes called juices. There are chemicals in these liquids that help break down the food. These chemicals are called enzymes. Each enzyme breaks down a particular food. In the saliva that attacks starch, in the stomach juice is an enzyme to attack protein while the pancreas produces enzymes to attack carbohydrates, proteins and fat. There are no enzymes to break down vitamins and minerals as they dissolve easily. There are other chemicals in the juices which help in digestion. In the stomach an acid is produced. This kills germs that may have been on the food when it was swallowed. The acid also helps the enzyme in the stomach to work. The liver makes a chemical rather like soap which splits up fat into tiny droplets. The fat digesting enzyme can attack these more easily that a large lump.

The food is completely broken down by the time it travels through the small intestine. This is the place where the digested food is taken into the blood. The lining of the small intestine is covered with thousands of tiny projections. They make the surface of the lining much larger than if it was just flat. The purpose of the large surface is to take in as much of the digested food as possible. When the digested food leaves the intestine it passes into the blood and is moved round the body to where it is needed.

Not all the material in food is digested. It passes onto the large intestine where water is removed from it. The semi-dry solid is then stored at the end of the large intestine until it is released when we go to the toilet.