Trachea

• The trachea, also called the windpipe, is the main airway passage that takes air to the lungs. The trachea, which is connected at the nose and mouth, is a bony, hollow tube in the front of the neck. This tube continues down the chest where it branches to the left and right lung.
  
  

Lobes

• The lungs are sectioned in lobes. The right lung is larger than the left, so it has more lobes. The right lung has three lobes, while the left lung only has two lobes. The left lung is smaller to compensate for the space taken by the heart. The heart rests between the right and left lung but is situated more on the left.
  
  

Bronchioles

• Bronchioles are structures that branch in the lungs. The bronchioles connect on one side at the trachea and terminate at the alveoli. The bronchioles carry the air to the alveoli, where gas exchange occurs. They are also the first step after the alveoli in bringing carbon dioxide out of the lungs when you exhale.
  
  

Alveoli

• The alveoli are tiny sacs responsible for gas exchange. These sacs hold air, but they are also surrounded by capillaries. The capillaries have a tiny wall and are filled with blood. The alveoli supply the blood with the oxygen that is inhaled. When you exhale, the blood exchanges carbon dioxide for oxygen. The carbon dioxide is then removed from the body.
  
  

Diaphragm

• The diaphragm is the muscle responsible for inflating and expanding the lungs. When your inhale, the diaphragm muscle contracts and presses the bottom parts of the left and right lung, causing the lungs to inflate. When you exhale, the diaphragm relaxes and the lungs are returned to their original shape.