Sinus

What is sinus? I started my searching right now though procrastinate hold me for two years back. I thought sinus was located all over in a human body in every bone that we have. This is kinda funny that the fact it is so tickling. But my guess was wrong and the sinus only present in the area of the face. At least I got the idea haha. (Jk)

So here is the definition, sinus is a cavity within a bone or other tissue, especially one in the bones of the face or skull connecting with the nasal cavities.

In common usage, "sinus" usually refers to the paranasal sinuses, which are air cavities in the cranial bones, especially those near the nose and connecting to it. Most individuals have four paired cavities located in the cranial bone or skull.

Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. 

1. Maxillary sinuses are located under the eyes; 
2. Frontal sinuses are above the eyes; 
3. Ethmoidal sinuses are between the eyes 
4. Sphenoidal sinuses are behind the eyes.