The human respiratory system is a series of organs responsible for taking in oxygen and expelling carbon dioxide. The primary organs of the respiratory system are lungs, which carry out this exchange of gases as we breathe.
The upper respiratory tract (upper airway) consists of the nose, mouth, sinuses, pharynx (upper section of the throat), and larynx (voice box). The lower respiratory tract consists of the trachea (windpipe), bronchial tubes, and lungs. The bronchial tubes carry air into the lungs and branch into smaller and smaller bronchioles which end in alveoli (air sacs).