There are a total of four hollow sinus cavities in the human head, which are all located in the skull, according to WebMD. The four distinct parts that make up the sinus cavities in the skull are the sphenoid, maxillary, ethmoid and frontal sinuses. All of these sinuses contain pink, soft tissue and are connected to one another to form a single system.
The Largest of the sinuses arethe maxillary sinuses, which are located in the cheekbones and are about one inch wide, according to WebMD. Positioned behind the nasal cavity are the sphenoid sinuses while the ethmoid sinuses are located in the middle of the nasal bridge and in between both eyes. The sinuses thatare located at the highest point in the skull are the frontal sinuses. The frontal sinuses are positioned between and on top of the eyebrows and in the bottom middle of the forehead.