We nose doctors spend a lot of our time talking to people about their sinuses. So, you might wonder, what ARE sinuses?
The word sinus really means a space. In medicine, we talk about several kinds of sinuses, but today we are going to be talking about the sinuses in the bones around the nose, the paranasal sinuses. These are, quite literally, air-filled spaces that have developed inside the bones of the face. There are four sets of paranasal sinuses on each side, named for the bones that they are within. All told, the total volume of all the sinuses put together is typically about 60 mL or about a quarter cup.
Most people know about the sinuses behind the cheeks below the eyes. These are the maxillary sinuses because they are in the maxillary bones. In most people, these are the biggest sinuses. They are more or less pyramid-shaped, with the base in front. The roof of the sinus is the same as the floor of the eye socket. The floor of the sinus is the same as the roof of the mouth, and the roots of the molars make bumps in the floor of the sinus. The inside of the sinus is the same as the sidewall of the nose. This sinus is one big space on each side, with a tiny passageway out into the nose.
The frontal sinuses are in the frontal bone, behind the forehead. These are fairly flat. The front wall is the forehead. Behind the back wall is the brain. There may be a single cavity on each side, or they may have a couple of dividers. These also have tiny communicating openings into the nose.
The ethmoid sinuses are between the eye sockets, and consist of about a dozen interconnected air cells, kind of like a piece of bubble wrap made of bone.
Behind the ethmoid sinuses are the sphenoid sinuses, which are essentially in the middle of the head. We usually have one on each side, with their tiny openings into the nose.
So, all of these sinuses are normally full of air. If their openings swell shut, bacteria get trapped inside and then a sinus infection happens. With an infection, the sinus can fill up with pus (YUCK!) or the lining tissue inside can thicken up and make it more likely to get future infections (ICK!).
Let me add here that if you irrigate your nose with saltwater, like with a Neti Pot or squeeze bottle, normally NONE of that saltwater goes into the sinuses. The openings are too small. The same is true for nose sprays. They don’t actually get INTO the sinuses. You can’t “wash out” your sinuses (unless you had an operation to make your sinus opening bigger).
Well…what are they doing there?
It is really hard to be sure. Certainly, in some people, they don’t develop, and the bones just stay solid. Those people seem to have no problems related to their lack of sinuses. And no sinus infections. Lucky ducks.
Some have said they are to make the face lighter. I don’t think so. The total weight of bone saved would be less than three ounces, in a head that weighs ten or eleven pounds.
Others say they are for voice resonance. In the late 1800’s someone decided to test this theory. They took an opera singer and had a panel of experts to judge him while singing an aria. They then filled up his sinuses with milk (Why milk? Who knows?) and judged him again on the aria. None of the experts could tell the difference.
The truly misinformed will tell you that they help filter the air. The problem is that essentially no air circulates in sinuses with breathing. Again, the openings are simply too small.
My favorite theory is that they are there to re-distribute the force of impact. If you hit a solid piece of bone, the force goes essentially straight through. If you hit a hollow bone, the force gets directed through the walls to the sides. So, if you get bopped in the forehead, less force will get to your brain if the forehead is hollow. Animals that butt heads, like bighorn sheep and deer, have GIGANTIC sinus systems. So maybe, we are simply meant to butt heads.
We love to help people with their sinuses. If you are having problems, make an appointment and come see us!
