Class 7 Biology Respiration in Organisms The process of breathing

The process of breathing

  • The process of breathing is very important for carrying out life. This process is carried out through the respiratory system of the body.
  • The air rich in oxygen in inhaled through the nostrils and is passed onto the nasal cavity where air is warmed and humidified by the mucus present in the nostril. The tiny hairs called ciliated epithelium filters out dust and other particles present in the air
  • The nasal cavity is divided into two halves left and right by a wall of thin bone known as central septum.
  • The air then passes through the windpipe also known as trachea. The trachea filters the air we inhale and branches into the bronchi.
  • The trachea further divides into bronchi.
  • Bronchi refers to two air tubes that carry the atmospheric air directly into the lungs.
  • Lungs are the pair of main organ of the respiratory system where oxygen is taken into and carbon dioxide is expelled out. The red blood cells present in the blood absorbs the oxygen present in the oxygen rich blood in the lungs.
  • They carry it and distribute it to all body cells and picks up the carbon dioxide produced by the cells.
  • This gaseous exchange takes place in a tiny sac like structure present in the lungs and is known as Alveolus.
  • Muscular sheets called diaphragm are also present in the chest cavity.
  • The process of breathing is accompanied by the movement of diaphragm and the rib cage.


  • During breathing in oxygen rich air the rib cage moves up and outwards whereas the diaphragm moves down.
  • This phenomenon expands the space available in the chest cavity which in turn makes the air get into lungs.
  • During breathing out air rich in carbon-dioxide the rib cage moves down and inwards whereas the diaphragm moves up.
  • This phenomenon reduces the space available in the chest cavity which in turn pushes out the air from the lungs.

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