Human Digestive System

Digestive System

The digestive system is the collective name used to describe the alimentary canal, some accessory organs and a variety of digestive processes.

• The complex of digestive processes gradually breaks down the foods eaten until they are in a form suitable for absorption.

• After absorption, nutrients are used to synthesise body constituents. They provide the raw materials for the manufacture of new cells, hormones and enzymes, and the energy needed for these and other processes and for the disposal of waste materials.

The activities in the digestive system can be grouped under five main headings.

• Ingestion = This is the process of taking food into the alimentary tract.

• Propulsion = This moves the contents along the alimentary tract.

• Digestion = This consists of:

➢ mechanical

breakdown of food e.g. mastication (chewing)

➢ chemical

digestion of food by enzymes present in secretions produced by glands and accessory organs of the digestive system.

• Absorption = This is the process by which digested food substances pass through the walls of some organs of the alimentary canal into the blood and lymph capillaries for circulation round the body.

• Elimination = Food substances which have been eaten but cannot be digested and absorbed are excreted by the bowel as faeces.

Organs of the Digestive system

1. Alimentary canal or Gastrointestinal tract (g.i.t.)

2. Accessory organs

1. Alimentary canal or Gastrointestinal tract (g.i.t.) :-

This is a long tube through which food passes. It commences at the mouth and terminates at the anus.

The parts are:

• Mouth or oral cavity

• Pharynx

• Oesophagus

• Stomach

• Small Intestine

• Large Intestine

• Rectum and anal canal

2. Accessory organs :-

Various secretions are poured into the alimentary tract, some by glands in the lining membrane of the organs, e.g. gastric juice secreted by glands in the lining of the stomach, and some by glands situated outside the tract. The latter are the accessory organs of digestion and their secretions pass through ducts to enter the tract. They consist of:

• 3 pairs of Salivary glands

• Pancreas

• Liver and Biliary tract

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