Sinus Anatomy:

Definition of Nasal Sinuses:

Nasal sinuses are hollow, air-filled spaces, within the bones of the skull and face. We possess four pairs of sinuses, and each sinus connects to the nasal cavity through small openings called ostium. Each sinus is named for the bone within which it is located:

• Maxillary Sinus - There is one maxillary sinus on each side of the nose, located under the eyes, in the cheeks.
• Ethmoid Sinus - There is approximately 6-12 small ethmoid sinuses on each side of the nose, between the eyes.
• Frontal Sinus - There is one frontal sinus on each side of the nose, located above the eyes, in the forehead.
• Sphenoid Sinus - There is one sphenoid sinus on each side of the nose, located behind the ethmoid sinuses near the middle of the skull, behind the eyes.

Importance of Nasal Sinuses:

Nasal sinuses are covered with a special lining similar to the lining in the nasal cavity called mucosa. This lining secretes mucus, a complex substance that keeps the nose and sinuses moist. The mucus also helps trap dust, viruses, and bacteria and removes them from the nose. The sinus mucosa is ciliated; that is, each cell on its surface has a cilium, a hair-like structure that has the capacity to push sinus mucus. This movement of mucus (which is known as mucociliary clearance) is responsible for clearing the sinuses and nasal cavity of substances trapped in the mucus.