The respiratory system

In addition to nutrients, we need oxygen to live. We breathe to obtain oxygen from the air.

This function is carried out by the respiratory system.It is made up of the nose, air passageways ( the tubes which carry air in and out of the body), and the lungs.

- First, the air enters through the nose. Then it passes through the pharynx, the larynx, and the trachea. Next, it goes through the two main bronchi and into each lung. In the lungs, the bronchi divide into smaller bronchioles. There are tiny sacs of air at the end of the bronchioles called alveoli.

-In the alveoli, oxygen from the air passes into the blood. The blood releases carbon dioxide which passes into the alveoli. It is toxic, and the body expels it.

Two movements, inhalation and exhalation, cause the air to circulate:
When we inhale, our lungs fill with air.
When we exhale, air leaves the lungs.