Nasal Cavity & Paranasal Sinuses

The nasal cavity is an air-filled space located within the nose. It has several functions including sensing smell, warming and humidifying inhaled air, trapping pathogens and particulate matter, and receiving drainage from the paranasal sinuses. The lateral walls of the nasal cavity contain three horizontal protrusions of bone on each side known as the superior, middle, and inferior turbinates. Below these turbinates are passages known as meatuses where air and fluid drain into the nasal cavity from the paranasal sinuses. The nasal cavity is bisected by the nasal septum, which consists of bone and cartilage. The septum has a rich vascular supply. The septal branch of the anterior ethmoidal artery, lateral nasal branch of the sphenopalatine artery, septal branch of the superior labial artery, and greater palatine artery connect in the anterior inferior quadrant of the nasal septum to form Kiesselbach's plexus, the most common site for anterior nosebleeds (epistaxis).

The paranasal sinuses are four paired, air-filled spaces within the cranial bones that connect to the nasal cavity. They are named after the bones in which they are located. There is the maxillary sinus within the maxillary bone, the frontal sinus, located behind the brow ridge in the frontal bone, the ethmoid sinus, situated medial to the orbital cavity and housing the ethmoidal air cells, and, finally, the sphenoid sinus which is located in the sphenoid bone.