by • 24/07/2011 • Old Pattern Biology NotesComments (0)634


First of all food comes in the oral cavity where the teeth crush and break the food and convert it into small particles. The tongue rolls the morsel of food and pushes it under teeth again and again so that the food is evenly divided into fine particles and the saliva secreted from the salivary glands gets mixed with the food. The saliva lubricates the food and makes the particles adhere to one another, forming a ball of food called bolus.

Now the chemical digestion of food begins. Saliva contains an enzyme to digest starch in the food. The combined action of teeth, tongue and saliva pushes the bolus through the throat into the oesophagus, and then it reaches the stomach.

Definition of Digestion

Digestion is the process in which the insoluble and non-diffusible components of food are broken down and by the action of enzymes are converted into soluble and diffusible substance to be absorbed into the blood stream.

Types of Digestion

1. Mechanical digestion

2. Chemical Digestion

·        Mechanical Digestion:

In mechanical digestion, the food consisting of large sized particle is broken into fine pieces by cutting, grinding, chewing and churning up, so that enzymes can act upon it efficiently and effectively. Mechanical digestion of food takes place in the mouth and stomach.

·        Chemical Digestion:

In chemical digestion, the digestive enzymes mix with the food and act upon it to break it down further into simple and diffusible chemical forms. The enzymes act on carbohydrates, proteins and fats separately. Chemical digestion takes place in all the major parts of the digestive system.

The digestive glands such as liver and pancreas also play very important role in this digestion.

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