A basic knowledge of the anatomy and physiology of the nose and sinuses is necessary to understand nasal and sinus disorders.
The nose and sinuses are a part of the upper respiratory tract. The three-dimensional anatomy of this area is complex. The function of the nose in addition to smell is to warm, humidify and filter air that passes through it. The external nose consists of a bony and cartilaginous framework. The nostrils, or anterior nares, form the external opening to the nose. The nasal septum is a midline internal structure that separates the left and right nasal cavities. It is composed of cartilage and bone. A deviated nasal septum can cause nasal obstruction.
There are four sets of paired sinuses. The maxillary sinuses are located beneath the cheeks and under the eyes. The frontal sinuses are above the eyes behind the forehead. The ethmoids are honeycomb shaped sinuses located between the eyes and the sphenoid sinuses are located behind the nose and below the brain. Each of these sinuses is an enclosed space that drains through an ostium or opening into the nose. The sinuses are lined by mucosa that is similar to the lining of the nose. These ostia can become blocked by inflammation or swelling of the mucosa as well as by tumors or bony structures.
The lateral nasal wall internally contains the three turbinate bones.These scroll-like structures are covered in a mucous membrane that contains vascular channels which can swell under certain conditions, such as allergy or inflammation. The tear duct or nasolacrimal duct drains tears from the eyes into the nose where it enters beneath the inferior turbinate. Blockage of this duct from injury or disease causes excess tearing of the eye, or epiphora. The middle meatus is a space under the middle turbinate. Within the middle meatus is the osteomeatal complex which is the common pathway for the drainage of the maxillary (cheek) sinus, frontal (forehead) sinus, and anterior ethmoid sinus. Inflammation or swelling of these key areas may cause blockage of the sinuses.
The superior turbinate is a small structure located high in the nose. Behind the superior turbinate is the opening of the sphenoid sinus, located near the back portion of the septum. The pituitary gland is located directly above and behind the sphenoid sinus. Pituitary surgery is performed through the sphenoid sinus.