Development, structure and function of the upper airways.

The upper airways play an essential role in the conduction of air into the lungs, and influence the properties of the inhaled air by both the anatomical structure and the functional properties of the mucosa, cartilages and neural and lymphatic tissues. The upper airways also play an important role in the protection of the lower airways, in the formation of the sound and host the sense of olfaction. Main events in the development of the upper airways happen during early embryonic periods. Postnatally, the growth of the airways follows the growth of the skeleton of the head and of the neck and thorax. Growth is accelerated mainly during the first 2 years of life; thereafter, it linearly follows the growth of the body. For a profound understanding of the function of the upper airways, it is important to understand the main developmental events during both prenatal and postnatal periods.