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 lungs' tertiary bronchi are also called the segmental bronchi. They branch out from the secondary bronchi, which descend from the mainstream bronchi. Lower in the lung, they become smaller and break up into the primary bronchioles. Each tertiary bronchus serves a particular bronchopulmonary segment.