Breathing System

Key Stage 3

The Breathing System is an organ system, that includes lungs, used to absorb Oxygen into the blood and remove Carbon Dioxide from the blood.

The Breathing System is specially adapted to exchange absorb Oxygen into the blood and remove Carbon Dioxide from the blood as quickly as possible.

The parts in the Breathing System that you should know:


A diagram showing the parts of the human Breathing System.

Air enters the mouth, travels down the trachea, through one of the bronchi, through a bronchiole and to an alveolus. Oxygen is transferred into the blood while Carbon Dioxide in the blood is transferred into the alveolus.

To breath the lungs must be able to take in new air and release the old air.

When the lungs take in air this is called inhalation.

When the lungs get rid of old air this is called exhalation.


To inhale the diaphragm contracts and goes down while the intercostal muscles contract pulling the ribs upwards and outwards. To exhale the diaphragm relaxes and goes up while the intercostal muscles relax allowing the ribs to go down and inward.


An animation of the lungs inhaling and exhaling.