Relating to the nose. The nasal bridge is the upper bony part of the nose. The nasal cavity consists of two large irregular air-filled spaces ( nasal vestibule) separated by a quadrilateral vertical septum ( nasal septum) with membranous, cartilaginous, and bony parts situated either side of the midline and extending from the cranial base to the roof of the mouth; it communicates anteriorly with the nostrils (anterior nares) and posteriorly with the nasopharynx. The nasal cavity is lined with mucous membrane containing olfactory receptors. The anterior nasal spine is a pointed forwards projection from the centre of the nasal part of the frontal bone; the tip (acanthion) is used as a cephalometric landmark. The posterior nasal spine is the sharp posterior extremity of the nasal crest at the rear of the palate.