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 Bronchial tree consists of bronchi, bronchioles, and alveoli. Bronchi are formed as the lower part of the trachea divides into two tubes. The primary portion enters the lungs at a region called the hilus. The primary branch forms a secondary branch, which then branches into smaller tertiary bronchi.ronchial Tree. Trachea is also known as the windpipe. It is a tube about 10-12.5 cm long (4-5 inches) and about 2.5 cm wide (1 inch). The trachea extends from the lower edge of the larynx downward into the thoracic cavity, where it splits into right and left bronchi. Rings of cartilage keep the airway open.