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.
Bronchi (singular: bronchus) Each bronchus leads to one of the lungs. Bronchi are air passage ways in the lungs. Within each lung, the large bronchi subdivides into smaller bronchi, which lead to even smaller air passageways called bronchioles. These continue to subdivide until they reach a series of dead ends were there are millions of tiny air sacs called alveoli.