The lungs are a pair of air-filled, spongy organs on either side of the chest (thorax). Every cell in the body requires oxygen to survive. Oxygen and other gases are found in the air we breathe. When oxygen reaches the lungs, it is transported to the bloodstream and carried throughout the body. Each cell in your body exchanges oxygen for the waste gas carbon dioxide. This waste gas is subsequently carried back to the lungs, where it is taken from the bloodstream and expelled.

Bronchioles are air passageways within the lungs that branch off like tree limbs from the bronchi, the two main air passages into which air flows after being inhaled through the nose or mouth. The bronchioles transport air to tiny sacs called alveoli, which exchange oxygen and carbon dioxide.

The trachea connects your larynx (voice box) to your bronchi. The bronchi transport air to the lungs. The trachea is an important component of your respiratory system. The trachea is made up of cartilage rings. It is bordered with mucus-producing cells.