Your lungs work nonstop to carry on the respiration that keeps you alive. Respiration is a single complete act of breathing.
The process begins when you inhale. Air passes through your mouth and nose into your trachea, or windpipe. The trachea splits into two main branches, or bronchi. One branch goes to the left lung, the other to the right lung. Once there, each bronchus (singular for bronchi) branches into smaller and smaller tubes, or bronchioles. The tiniest tubes end in grapelike sacs called alveoli.
Each alveolus (singular for alveoli) is covered in a net of tiny blood vessels. These are called capillaries. Respiration happens between the alveoli and the capillaries. It is the gas exchange between the blood in the pulmonary (lung) capillaries and the air within the alveoli.
