2. Airways: The airways are a system of tubes that carry air to and from the lungs. The main airways are the trachea (windpipe), the bronchi, and the bronchioles. The trachea is a large tube that connects the larynx (voice box) to the lungs. The bronchi are the two large branches of the trachea that enter the lungs. The bronchioles are the smaller branches of the bronchi that lead to the alveoli.
3. Respiratory muscles: The respiratory muscles are the muscles that are used to breathe. The main respiratory muscles are the diaphragm and the intercostal muscles. The diaphragm is a large muscle that separates the chest cavity from the abdominal cavity. The intercostal muscles are the muscles that run between the ribs.