The sinuses are pockets for air within the bones of the face. They are usually hollow, and they surround the nose. There are four pairs of sinuses, and they are named after the facial bones in which they are located.
- The maxillary sinuses are below the eyes and tucked into the upper cheek bones.
- The frontal sinuses are above the eyes and nose within the forehead.
- The ethmoid sinuses are located within the bones behind the eyes, and they are composed of a complex system of air cells further broken down into anterior and posterior ethmoid sinuses.
- Tucked behind the ethmoid sinuses are the sphenoid sinuses.
Although the sinuses are walled-off enclosures, all of the sinuses also have an ostium, or opening. Each sinus produces mucus, and it drains naturally through the ostium to clean the sinuses and nasal passageways.
Separating the right and left nares is the nasal septum. The septum divides the nose into left and right sections. It is made of cartilage in the front and bone in the back, and it is encased with mucous membrane. Many people have a deviated septum, which can block the nose and sinuses from their usual functions.
Further within the nose, one can see the turbinates. They are bony growths on the lateral nasal walls, and they increase the surface area of the nose. There are inferior, middle, and superior turbinates on the right and left sides of the nose, and each turbinate has a meatus, or cleft, underneath it. They direct the flow of the nasal passages. The inferior meatus drains the nasolacrimal duct, which collects tears from the eyes. The middle meatus collects drainage from the maxillary, anterior ethmoid, and frontal sinuses. The superior meatus is used by the posterior ethmoid sinuses. Across from the superior meatus is the sphenoethmoid recess, and the sphenoid sinuses drain into there.
Nasal and Sinus Functions
The nose and sinuses perform important roles for the body and intake of air. They filter air that is breathed in, warm it, and add moisture to it. The ideal function of the nose is to adapt the air to an appropriate temperature for the body, make it the correct amount of moisture, and purify the air.
The nose and sinuses produce mucus, which can capture bacteria and foreign particles to protect the respiratory system. The nasal passageways are lined with cilia, a small, hair-like structure that move the mucus throughout the upper respiratory system. The cilia create a defense against germs by moving those pathogens and allergens out of the system.
The nose is also responsible for the sense of smell, or olfaction. There are receptor cells that detect scents located in the upper portion of the nose just below the bone separating the nose from the brain. Sinuses can also soften some of the blow from a head injury, and they play a crucial role in the sound and tone of speech.