1. Digestion is the process by which food is broken down into soluble substances that can be absorbed in the blood stream.
  2. Digestion starts from the mouth and ends in the


          There are two types of digestion;

  1. Mechanical digestion.
  2. Chemical digestion

Mechanical digestion

  1. This is the process of breaking down food into small particles by the help of teeth.
  2. It takes place in the mouth in human beings.

Chemical digestion.

  1. This is the process of breaking down food by the help of chemical compounds called
  2. Chemical digestion starts in the mouth and ends in the ileum.
  3. Enzymes are chemical substances that speed up the rate of digestion.

Characteristics of enzymes.

  1. They are protein in nature.
  2. An enzyme always forms the same end product.
  3. They are specific i.e. each enzyme acts upon one class of food.
  4. They are destroyed by heating.
  5. They act in particular conditions i.e. some prefer acidic, others alkaline

 Conditions under which enzymes work.

  1. They work best in temperatures below 40o
  2. They can easily be destroyed by heat above 40o c
  3. Pepsin and rennin work best in acidic conditions.
  4. Trypsin, amylase, lipase and intestinal enzymes work best in alkaline conditions. 


The alimentary canal.

  1. The alimentary canal is a muscular tube that runs from the mouth to the anus.
  2. The alimentary canal is about ten metres in an average adult person.

Parts of the alimentary canal.

  1. Mouth
  2. Gullet (oesophagus)
  3. Stomach
  4. Small intestine.
  5. Large intestine
  6. Rectum
  7. Anus