The Gaseous Exchange System

Gas Exchange in Mammals

• In mammals, the lungs are gas exchange organs.
• They help to get oxygen into the blood (for respiration) and to get rid of carbon dioxide (made by respiring cells) from the boyd. 

Structure of the gaseous exchange system

• As you breathe in, air enters the trachea (windpipe) 
• The trachea splits into two bronchi - one bronchus leading to each lung. 
• Each bronchus then branches off into smaller tubes called bronchioles.
• The bronchioles end in small 'air sacs' called alveoli. 
• This is where gases are exchanged.
• The ribcage, intercostal muscles and diaphragm all work together to move air in and out. 

Alveoli

• These form the gas exchange surface.
• Alveoli are arranged in bunches at the end of the bronchioles. 
• They are surrounded by a network of capillaries, giving eah alveolus its own blood supply.

Alveoli Structure

• Each alveolus is made from a single layer of thin, flat cells…