What is Paranasal sinuses?
[[Image:X-Ray Skull.jpg|thumb|200px|Sinuses sideways-on in an [[X-ray]] image]] '''Paranasal sinuses''' are parts of the [[nasal cavity]].<ref>Fehrenbach and Herring 2012. ''Illustrated anatomy of the head and neck'', Elsevier, p 68.</ref> They are usually counted to be part of the [[respiratory system]]. They are [[mucous membrane]]s, which are mostly inside [[bone]]s. These bones are then filled with air, which makes the skull look bigger, without adding much extra weight. Prenasal cavities can be found in [[mammal]]s, most [[bird]]s, [[dinosaur]]s, and [[crocodilia]]ns. Since sinuses are in virtually all land [[vertebrates]], they must have a function. They are covered with a [[mucosa]], [[epidermis|epidermal]] cells which are moist and make [[mucus]]. This moistens and warms the air on its way into the [[lungs]]. The mucus also picks up particles which come in with the air. A variety of possible functions have been proposed: * Decreasing the relative weight of the front of the skull, and especially the bones of the face. * Increasing resonance of the [[voice]]. * Providing a buffer against face damage. * Insulating sensitive structures like dental roots and eyes from rapid temperature fluctuations in the nasal cavity. * Humidifying and heating of inhaled air because of slow air turnover in this region. * Regulation of intranasal and serum gas pressures. * Immunological defence. == References == {{reflist}} {{-}} {{science-stub}} [[Category:Head (body part)]]