These photographs will help you review the basic structures of the respiratory system. The trachea is the airway into the thoracic cavity. The bronchi (sing: bronchus) branch from the trachea and each leads into one of the two lungs, where they subdivide to become a series of bronchioles. Bronchioles, in turn, become alveolar_ducts, alveolar_sacs, and alveoli (sing: alveolus).

The diaphragm is a band of skeletal muscle. Its cycle of contraction and relaxation changes the pressure in the thoracic cavity, thereby facilitating breathing.

The cat's lungs have several lobes. The right lung has four lobes: anterior, middle, posterior, and mediastinal. The left lung has only three lobes: anterior, middle, and posterior.