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.
Within the lungs, the left and right bronchus divide into smaller tubes called the secondary bronchi. There are 2 of these on the left side and 3 on the right. Each secondary bronchus divides into smaller tubes called bronchioles.