Gas exchange or respiration takes place at a respiratory surface, a boundary between the external environment and the interior of the body.
A respiratory epithelium is the area across which gas diffusion occurs. These surfaces depend on rapid diffusion and must consist of moist, living cells (gases dissolve in water). Epithelial cells moisten and protect the airway.
A chronic obstructive pulmonary disease characterized by the decreased elasticity of lung tissue.
Surgical procedures on the neck to open a direct airway through an incision in the trachea.