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 respiratory system consists of several organs, including the mouth, nose, larynx, pharynx, trachea and the lungs. The larynx is the voice box, the pharynx is the throat and the trachea is the windpipe. The esophagus and trachea, not part of the respiratory system, occupy an area that is located between the two lungs.