1. The mouth performs two functions: 1
The mouth performs two functions: 1. Mechanical digestion involves chewing – teeth chop and grind food into small pieces. 2. Mixing food with saliva saliva starts the break down of carbohydrates (starch) using an enzyme called amylase.
The Mouth
Amylase

2. The Oesophagus
After being swallowed the food travels down the oesophagus.

3. The Stomach
The stomach continues to mix the food with digestive enzymes. Amylase continues to digest carbohydrates Proteins are digested in the stomach and small intestine. Protease enzymes break down proteins into amino acids. Digestion of proteins in the stomach is helped by stomach acid, which is strong hydrochloric acid. This also kills harmful micro-organisms that may be in the food. O
Protease

4. Small Intestine Lipase
Lipase enzymes break down fat into fatty acids and glycerol. Digestion of fat in the small intestine is helped by bile, made in the liver. Bile breaks the fat into small droplets that are easier for the lipase enzymes to work on.
Lipase

5. The Small Intestine- Microvilli
The inside of the intestine is folded and covered in microvilli. The microvilli increase the surface area of the intestine to increase the absorption of carbohydrates, amino acids and fats

6. By the time food reaches the large intestine all useful nutrients have been absorbed into the blood. All that remains are waste products of digestion and water. The water is very valuable so is absorbed into the blood stream Waste products pass through the large intestine to be stored in the rectum before passing out of the anus as faeces.
Large Intestine
The appendix is used to help some animals digest cellulose in plants. In humans the appendix has a very limited role as humans do not need to digest cellulose for carbohydrates.

7. Liver and Pancreas
The pancreas produces chemicals called digestive enzymes such as:
Protease - proteins
Carbohydrase (amylase) - carbohydrates
Lipase - fats
The liver and the pancreas play important part in digestion. The liver produces bile, which helps the digestion of fat.