Paranasal sinuses. Rotating animation of the paranasal sinuses in a transparent model of the head. The paranasal sinuses are spaces in the bones surrounding the eyes and nose, and the cheek bones of the upper jaw. They lighten the bones of the skull and reduce the weight of the head. They are connected to the nasal passages and are lined with mucous membranes. The paranasal sinuses are: the frontal sinus (in forehead), the ethmoid sinus (either side of eyes), the sphenoid sinus (behind the ethmoid) and the maxillary sinus (in the cheeks).HD master is flattened onto a black background, as seen in this preview. The original file has a transparent alpha channel and is available as the HD master of clip K003 3734.