How do the lungs, bronchi, and trachea interact?
The diaphragm is a sheet of muscle that spreads across the bottom of the rib cage. When the diaphragm contracts, chest volume increases, and the lungs take in air. The lungs are the organs of the respiratory system in which gas exchange takes place between the blood and the atmosphere. The trachea, or wind pipe, is a long tube that leads down to the chest. The trachea divides as it enters the lungs to form the right and left bronchi. The bronchi branch into bronchial tubes, which branch into small bronchioles. Bronchioles are the smallest branches of the air passages in the lungs. The bronchioles deliver air to and from tiny sacs called alveoli at their tips. The alveoli are where oxygen and carbon dioxide are exchanged.