You’ve most likely had a sinus infection, or known someone who has, but what exactly are sinuses?
Well, humans have several air-filled spaces within the skull around the face. These bony cavities, called “paranasal sinuses,” are lined with mucous membrane, much like the lining of your nose and other air passageways. When the linings become swollen or produce lots of mucous, pressure builds up. This is one cause of “sinus headaches.”
It seems logical that we would be better off if our skulls were solid bone, so we’d never have sinus congestion or pressure headaches, right?
Well, the biological function of the sinuses is not entirely clear, but there are a few good hypotheses. Sinuses can act as air conditioners, humidifying and warming the air you breathe through your nose. Sinuses may also have evolved as a lightweight way to increase the strength of your skull, kind of like corrugated cardboard.
The air pockets may also act as crumple zones that can absorb the energy from a blow to the face, and protect the brain from injury. Finally, the sinuses are involved in the resonance properties of your voice. When you speak or sing, sound reflects off the interior surfaces of your sinus cavities. No two people have sinuses exactly alike in shape and size, so different resonances may allow us to discern one person’s voice from another.