Amino Acid-A building block of protein. Protein in food is broken down into amino acids during digestion and then reassembled into new proteins in the body.

Anus-The opening at the end of the digestive system through which faeces leave the body.

Bile-A yellow-green liquid that helps break down fats in the small intestine. Bile is made in the liver and stored in the gall bladder.

Carbohydrate-Substance that is an important source of energy. Simple carbohydrates, or sugars, include glucose. Complex carbohydrates, such as starch, are found in bread, pasta, rice and potatoes. Starch is broken down into glucose during digestion.

Duodenum-The first part of the small intestine.

Enzyme-A chemical that takes part in chemical changes in the body without being changed itself. Different enzymes help to break down and digest different kinds of food.

Faeces-undigested waste that passes through the large intestine and leaves the body through the anus.

Fat-Substance that is a source of energy and is also used by the body to insulate it and keep it warm. Dairy products, red meat and vegetable oils are all rich in fats.

Fatty acids-Substances that combine with glycerol to make fat.

Gallbladder-small bag or sac in which bile is stored.

Gastric Juice-Digestive juice produced by the glands in the lining of the stomach.

Gland-an organ or part of the body that produces something useful, such as digestive juice.

Glucose-A type of sugar produced when carbohydrates are digested. Within each body cell, glucose combines with oxygen to produce energy.

Glycerol-one of the substances that make up fat.

Glycogen-the form in which glucose is stored in the liver and muscles. Glycogen is changed back into glucose when the level of glucose in the blood drops.

Intestines-this tube joins the stomach to the anus.

Oesophagus-the pipe that takes food from the mouth and throat to the stomach.

Palate-the roof of the mouth. It is hard at the front and soft at the back of the mouth.

Pancreas-A large gland which produces digestive juices containing several enzymes.

Peristalsis-Contractions of the muscles in the oesophagus and intestines that squeeze food through the digestive system.

Protein-Substance that eh body needs to grow and to repair and maintain cells. Fish, eggs, cheese, meat and beans are all rich in proteins.

Starch-A carbohydrate made in plants and broken down during digestion to become glucose.

Urea-Waste substance made in the liver and filtered out of the blood in the kidneys.

Urine-A liquid made of urea and other waste substances dissolved in water. Urine is produced in the kidneys and stored in the bladder.

Valve-A device that allows liquid to flow in one direction only.