Upper Respiratory Tract

The esophagus is directly posterior to the trachea, and the cervical spine is posterior to the esophagus. The thyroid gland is anterior to the trachea. The pharynx is superior to both the trachea and the esophagus.

The pharynx is made up of three divisions: the laryngopharynx, the oropharynx, and the nasopharynx. There is no portion of the pharynx called the sinopharynx.

The frontal sinuses are not present at birth. They begin to develop in the first few years of life, but they are not fully mature until after adolescence. The sphenoid, maxillary, and ethmoid sinuses are present at birth, though they are underdeveloped and similarly do not mature fully till late childhood or adolescence.

The only chamber of the upper respiratory tract that is shared by both the respiratory and the digestive systems is the pharynx. The pharynx is the part of the throat that is immediately posterior to the mouth and the nasal cavity, and superior to the trachea, larynx, and esophagus.

The small flap of cartilage that covers the windpipe to prevent aspiration during swallowing is the epiglottis. It is located at the base of the tongue and attached to the entrance of the larynx.

The lumen of the trachea is maintained by the tracheal cartilages, a set of approximately 20 separate c-shaped rings of hyaline cartilage. The non-continuous cartilage allows for greater flexibility during inspiration and expiration.

The epithelium of the trachea is made up of pseudostratified columnar cells with cilia and goblet cells.

The trachea bifurcates into the left and right primary bronchi. This occurs at a location called the carina, which is at the level of T4-T5.

The only sinuses that can be assessed on physical exam are the frontal and maxillary sinuses. The sphenoid and ethmoid sinuses are too deep in the skull to be assessed via physical examination.