What is the anatomy of the upper airway in humans?

The anatomy of the upper airway consists of the pharynx and the nasal cavities, although some definitions also include the larynx and trachea. The pharynx is further divided into the nasopharynx, oropharynx, and laryngopharynx.

The nose is a pyramidal structure divided by a mid-line septum that separates the nasal cavities. Mucosa lines the nasal cavities and serves to heat and humidify gas during inhalation. The nasal cavity attaches to the paranasal sinuses, which drain directly into the nasal cavity and the posterior portion of the mouth, which opens into the oropharynx. The pharynx is a fibromuscular tube bounded anteriorly and superiorly by the nasal cavity andextending from the bottom of the skull to the cricoid cartilage. The epoglottis is a flap of elastic cartilage that guards the opening to the glottis.

Beyond the glottic inlet is the larynx, which is bounded by the aryepiglottic fold as well as the top of the epiglottis and the lower border of the cricoid cartilage. The larynx extends posteriorly into the laryngopharynx, creating a noticeable bulge. The trachea lies beyond the cricoid cartiage and consists of a tube formed by a set of cartilaginous rigs that extend down to the carina before branching off into the left and right mainstem bronchi.