| nuchal plane | <anatomy> The external surface of the squamous part of the occipital bone below the superior nuchal line, giving attachment to the muscles of the back of the neck. (05 Mar 2000) |
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| highest nuchal line | A line above and parallel to the superior nuchal line on the external surface of the occipital bone; it gives attachment to the epicranial aponeurosis and occipitalis muscle. Synonym: linea nuchae suprema. (05 Mar 2000) |
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| nuchal | <anatomy> Of, pertaining to, or in the region of, the back, or nape, of the neck; applied especially to the anterior median plate in the carapace of turtles. Origin: Cf. F. Nucal. Source: Websters Dictionary (01 Mar 1998) |
| nuchal fascia | <anatomy> The fascia that encloses the posterior muscles of the neck. Synonym: fascia nuchae. (05 Mar 2000) |
| nuchal ligament | A sagittal ligamentous band at the back of the neck, formed of thickened supraspinous ligaments; it extends from the external occipital protuberance to the posterior border of the foramen magnum, cranially, to the seventh cervical spinous process, caudally. Synonym: apparatus ligamentosus colli, nuchal ligament. (05 Mar 2000) |
| nuchal region | The back of neck, including the suboccipital region. Synonym: regio nuchalis, nuchal region, posterior neck region, regio cervicalis posterior. (05 Mar 2000) |
| nuchal rigidity | <neurology> Resistance to flexion of the neck, seen in individuals with meningitis. (27 Sep 1997) |
| nuchal tubercle | The vertebra in the cervicothoracic region which has the most prominent spinous process (seventh cervical vertebra in 70% of the cases, sixth in 20%, and first thoracic vertebra in 10%). Synonym: nuchal tubercle. (05 Mar 2000) |
| superior nuchal line | The ridge that extends laterally from the external occipital protuberance toward the lateral angle of the occipital bone; it gives attachment to the trapezius, sternocleidomastoid, and splenius capitis muscles. Synonym: linea nuchae superior. (05 Mar 2000) |
| dementia-nuchal dystonia | A disorder that is associated with nerve cell destruction and progressive lack of coordination, neck stiffness, trunk stiffness, problems with eye movement and mild dementia. Disorders that are similar include Alzheimer's disease, cerebellar dysfunction, Jakob-Creutzfeldt disease and Parkinson's disease. The cause for progressive supranuclear palsy is unknown, but is likely a degenerative nerve disorder that is somehow triggered by a viral infection. Pathologic changes include nerve cell damage and destruction of myelin sheath. There is no known cure. (27 Sep 1997) |
| inferior nuchal line | A ridge that extends laterally from the external occipital crest toward the jugular process of the occipital bone. Synonym: linea nuchae inferior. (05 Mar 2000) |
| Aeby's plane | In craniometry, a plane perpendicular to the median plane of the cranium, cutting the nasion and the basion. (05 Mar 2000) |
| aperture plane | <microscopy> In a microscope adjusted for Koehler illumination, the conjugate planes that include the light source, the condenser iris diaphragm, the objective lens back aperture, and the eye point. Spaces in the aperture planes are the reciprocal of those in the field planes. (05 Aug 1998) |
| auriculo-infraorbital plane | A standard craniometric reference plane passing through the right and left porion and the left orbitale; drawn on the profile radiograph or photograph from the superior margin of the acoustic meatus to the orbitale. Synonym: auriculo-infraorbital plane, eye-ear plane, Frankfort horizontal plane, Frankfort plane, infraorbitomeatal plane. (05 Mar 2000) |
| axial plane | Transverse plane, as in CT scanning. Synonym: transaxial plane. (05 Mar 2000) |
| axiolabiolingual plane | A plane parallel to the long axis of a tooth and extending in a labiolingual direction. (05 Mar 2000) |