The sphenoid sinus (sinus sphenoidalis) is located in the body of the sphenoid bone. The lower wall of the sinus participates in the formation of the wall of the nasal cavity. The cavernous sinus is adjacent to the upper part of the lateral wall.
The frontal sinus (sinus frontalis) varies considerably in size. The septum dividing the frontal sinus into right and left parts is usually asymmetrical.