DID YOU KNOW THAT...
Paranasal sinuses are air-filled cavities in the cranial bones lined with the mucous membrane. They have several important functions: cleaning and heating the inhaled air, reducing the weight of skull bones and even modulating the sound of our voice.
Sinuses are connected with the nasal cavity through narrow canals, called sinus ostia. In healthy sinuses the produced mucus is transported through the ostia to the nasal cavity and then down to the throat, where it is swollen. We do not notice this process.