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.
The human trachea (windpipe) divides into two main bronchi (also called mainstem bronchi), at the anatomical point known as the carina. The right main bronchus is wider and shorter than the left main bronchus. The right main bronchus subdivides into three lobar bronchi and the left main bronchus divides into two.