Respiratory tract, nasal cavity, trachea, cheekbones in adults. Representation of the airways in a man's silhouette, head in profile. We distinguish the nasal and oral cavities, the larynx followed by the trachea, bronchi and bronchioles. The pulmonary alveoli are not symbolized here. The airways are visible through transparency in both lungs. The lungs are shown in full with the fissures delimiting the upper, middle and lower lobes for the left lung. Whereas the right lung has only two lobes, upper and lower. The dome formed by the diaphragmatic dome constitutes the floor of the thoracic cavity containing the lungs. The diaphragm causes breathing in and out by contracting and relaxing.