Cranial sinuses are air-filled spaces located within the bones of the skull. They are lined with mucous membranes and play a role in reducing the weight of the skull, enhancing voice resonance, and providing insulation for the brain. The main cranial sinuses include the frontal sinus, maxillary sinus, ethmoid sinus, and sphenoid sinus. These sinuses are connected to the nasal cavity, allowing for the drainage of mucus and the regulation of air pressure. Inflammation or infection of the sinuses, known as sinusitis, can lead to symptoms such as facial pain, congestion, and headaches. Proper functioning of the cranial sinuses is essential for overall respiratory health.