• The five stages of digestion are ingestion, digestion, absorpbtion, assimilation and egestion.
  • Ingestion is the taking of food into the mouth.
  • Digestion is the breaking down of food.
  • Absorpbtion is the absorpbtion of molecules of food into the blood in the small intestine.
  • Assimilation is the taking of food molecules from the blood into body cells.
  • Egestion is the passing of undigested food out of the body.
  • Physical digestion involves the chewing of food in the mouth and churning of food in the stomach.
  • The four types of teeth are incisors, canines, premolars and molars.
  • Chemical digestion is the breaking down of food by enzymes.

The Digestive System

  • The digestive system is a group of organs working together to break down food and absorb the nutrients from it.
  • The mouth chews food and mixes it with enzymes, eg amylase in syliva.
  • The oesophagus carries food to the stomach by muscular action (peristalsis).
  • The stomach stores and churns food and mixes it with digestive juices. It also produces hydrochloric acid to kill bacteria.
  • The liver produces bile to break down fats.
  • The small intestine contains enzymes to break down food. Food molecules are absorbed into the blood in the small intestine.
  • The pancreas produces enzymes.
  • The large intestine passes water into the blood.


  • An enzyme is a chemical which speeds up a chemical reaction in the body without being used up in the reaction.
  • An enzyme acts on a substrate to produce the product.
  • Amylase is an enzyme which breaks down starch into maltose.