Respiratory system, nasal cavity, trachea, pommons, alveoli. Representation of the airways in a man silhouette, head in profile. We distinguish the nasal and oral cavities, the larynx followed by the trachea, from the bronchi and bronchioles to the alveoli. The airways are visible in the left lung in section. The right lung is shown in full with its two fissures delimiting the upper, middle and lower lobes. We can also distinguish the ganglion chain around the trachea (in green). Alveolar blood circulation is represented at the level of the 3 alveoli present in the left lung.