In humans the respiratory tract is the part of the anatomy involved with the process of respiration. The respiratory tract is divided into 3 segments: Upper respiratory tract: nose and nasal passages, paranasal sinuses, and throat or pharynx Respiratory airways: voice box or larynx, trachea, bronchi, and bronchioles Lungs: respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli The respiratory tract is a common site for infections.