The palatine tonsils are collections of lymphoid tissue on each side of the oropharynx in the interval between the palatine arches. The tonsil does not fill the tonsillar sinus (fossa) between the palatoglossal and palatopharyngeal arches in adults. The submucosal tonsillar bed, in which the palatine tonsil lies, is between these arches. The tonsillar bed is formed by the superior pharyngeal constrictor and the thin, fibrous sheet of pharyngobasilar fascia. This fascia blends with the periosteum of the cranial base and defines the limits of the pharyngeal wall in its superior part.