How do the lungs work?
The main function of the lungs is to take in oxygen, which is vital to the function of every cell in the body, and to remove carbon dioxide, a waste product. The respiratory system begins at the nose and mouth – inhaled air passes through the throat into the windpipe (trachea), which divides into two main airways that enter the left and right lung. The larger airways (bronchi) repeatedly branch off, becoming narrower and narrower (bronchioles).
- The lungs as part of the respiratory system
At the end of the smallest airways are about 300 million air sacs (alveoli), which are surrounded by a mesh of many tiny blood vessels (capillaries). Alveoli are lined with cells called epithelial cells, which make substances such as mucus.
- Gas exchange between capillaries and alveoli
Gas exchange takes place between the capillaries and the alveoli: Inhaled oxygen moves out of the alveoli into the capillaries, where it is taken up by red blood cells and distributed throughout the body. Carbon dioxide moves in the opposite direction: Brought by red blood cells from other parts of the body to the lungs, carbon dioxide moves out of the red blood cells and into the alveoli, where it leaves the body during exhalation.
Written by: Claudia Sarkady
Last updated: 30 July 2011
Sources: The Respiratory System, Edited by Kara Rogers, Britannica Educational Publishing, 2011