A natural opening or hole usually in bone. The apical foramen is the small opening at the apex of a tooth root through which nerves and blood vessels pass. The foramen caecum is a small depression on the dorsum of the tongue situated at the apex of a V-shaped groove (sulcus terminalis). The foramen magnum is a large aperture in the occipital bone in the base of the skull, through which passes the spinal cord. The incisive (nasopalatine) foramen is located in the midline, palatal to the maxillary incisors at the junction of the premaxilla and maxillae; it contains the nasopalatine blood vessels and nerve. The mandibular foramen is located on the medial aspect of the ramus of the mandible and contains the inferior alveolar (dental) nerve and inferior alveolar blood vessels. The mental foramen is located on the lateral aspect of the body of the mandible, usually between the first and second premolar and inferior to their root apices. It is a circular opening through which pass the mental nerve and blood vessels. When teeth and associated alveolar bone are lost, the foramen may be located beneath the fitting surface of a denture base. See appendix B for full list of foramina of the skull Foramina and canals of the bones of the skull.