Human digestive system

Alimentary canal

Alimentary canal

The human alimentary canal is where food is processed for use in the body. Different sections of the canal carry out different functions.

Lower small intestine

Ileum

Upper small intestine

Duodenum

Mouth

• food is taken in through the mouth

• Teeth break up food into small pieces

• Saliva breaks down the starch in the food down using salivary amylase

Stomach

• Stomach acid kills off harmful microbes

• Proteases digest proteins into amino acids

• It contracts to break down the food particles into smaller pieces

Pancreas

The pancreas secretes enzymes into the small intestine

• Carbohydrases

• Proteases

• Lipases

Small intestine

• Absorption of food involves the movement of small food molecules through the wall of the small intestine into the blood.

• The walls of the small intestine are covered in structures called villi which provide a large surface area for absorption.

Large intestine

• In the large intestine, water is absorbed through the walls of the large intestine into the blood.

• After water has been absorbed through the large intestine, undigested food leaves the body as faeces through the anus

The upper part is the colon and the lower is the rectum.

Liver

The liver produces bile which helps to neutralise stomach acid and emulsify fats which makes it easier to be absorbed and for enzymes to do their job. Bile is stored in the gall bladder. It is released into the small intestine.