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CSEC Biology: The Digestive System/Alimentary Canal

Updated: May 15, 2020

Digestion is the process by which the large, complex, insoluble food materials ingested are broken down by a series of mechanical and chemical processes into soluble forms which can be absorbed into the blood and used by the cells of the body. The substances ingested into the body are usually in their larger, complex molecular forms, for example proteins, starch (carbohydrates) and fats as a constituent unit of the larger food product. However, for these materials to be utilized by the body, they must be broken down into simpler forms by the digestive system.

Digestion, therefore, is an essential process which breaks down nutrients (useful substances in food) from the complex polymeric forms to their simpler monomeric forms. This occurs through mechanical digestion and chemical digestion (including hydrolysis and the action of enzymes).


As previously stated, digestion occurs in two parts. It begins with mechanical digestion, which is followed by chemical digestion.


Mechanical Digestion

Mechanical digestion is the physical breakdown of food into smaller bits and pieces to increase the surface area on which digestive enzymes can act.

Mechanical digestion begins in the mouth where it is carried out by the teeth.