Most WHO departments have their own procedures for supporting research in priority areas-these vary from requesting letters of intent to issuing a call for proposals to commissioning research.
In humans and other mammals, the anatomical features of the respiratory system include trachea, bronchi, bronchioles, lungs, and diaphragm. Molecules of oxygen and carbon dioxide are passively exchanged, by diffusion, between the gaseous external environment and the blood.
A bronchus is either of the two major branches of the trachea that lead to the lungs. The bronchi begin when the trachea divides to form the right and left main bronchi (pleural of bronchus.) These bronchi, in turn, travel to each of the lungs. The bronchi divide first into lobar bronchi and then tertiary bronchi.