upper respiratory tract

The upper respiratory tract is the entrance hall of the breathing system — the part above the voice box where air is first taken in, warmed, moistened and filtered before it heads deeper. It is the territory of the everyday cold, the stuffy nose and the sore throat.

Anatomically it usually means the nose and nasal cavity, the paranasal sinuses, the pharynx (the throat behind the nose and mouth), and the upper part of the larynx. These structures condition incoming air and trap dust and germs on their moist, hairy linings before the air reaches the delicate lungs.

The dividing line between upper and lower tract is conventionally drawn at the larynx, though sources differ on exactly which part of the larynx belongs where. Clinically the distinction matters because upper-tract infections (colds, sinusitis, pharyngitis) are usually mild and self-limited, while lower-tract infections (bronchitis, pneumonia) tend to be more serious.