| C3 | third cervical nerve; third cervical vertebra; third component of complement |
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| C4 | fourth cervical nerve; fourth cervical vertebra; fourth component of complement |
| C5 | fifth cervical nerve; fifth cervical vertebra; fifth component of complement |
| C6 | sixth cervical nerve; sixth cervical vertebra; sixth component of complement |
| C7 | seventh cervical nerve; seventh cervical vertebra; seventh component of complement |
| vacuum disk phenomenon | The appearance of a radiolucent stripe in an intervertebral disk, a manifestation of disk degeneration; a misnomer since there is gas present. (05 Mar 2000) |
|---|---|
| radioulnar articular disk | The disk that holds together the distal ends of the radius and ulna; it is attached by its apex to a depression between the styloid process and distal surface of the head of the ulna, and by its base to the ridge separating the ulnar notch from the carpal surface of the radius. Synonym: discus articularis radioulnaris, radioulnar disk, radioulnar articular disk, triangular cartilage, triangular disk of wrist, triquetrous cartilage. (05 Mar 2000) |
| Ramsden disk | <microscopy> The small circular patch of light that appears at the eyepoint above the ocular lens. This is the exit pupil of an optical instrument that, in a microscope adjusted for Koehler illumination, lies in a plane conjugate with the objective rear focal plane, condenser iris, and light source. Alteration of the Ramsden disk (for example, by the observer's iris) modifies the aperture function, diffraction pattern, and direction of view of the specimen. (05 Aug 1998) |
| mandibular disk | The fibrocartilaginous plate that separates the joint into upper and lower cavities. Synonym: discus articularis temporomandibularis, mandibular disk, temporomandibular articular disk. (05 Mar 2000) |
| germinal disk | Germ disk, the point in a telolecithal ovum where the embryo begins to be formed. Synonym: embryonic disk, germinal area, area germinativa. (05 Mar 2000) |
| Merkel's tactile disk | A specialised tactile sensory nerve ending in the epidermis, characterised by a terminal cuplike expansion of an intraepidermal axon in contact with the base of a single modified keratinocyte. Synonym: meniscus tactus, Merkel's corpuscle, Merkel's tactile cell, Merkel's tactile disk, tactile disk. (05 Mar 2000) |
| choked disk | papilloedema |
| micrometre disk | <microscopy> A glass disk engraved with a suitable scale, used at the diaphragm of a micrometre ocular. The scale to be focused by the eye lens has to be seen in the field of view. Micrometre eye piece. (05 Aug 1998) |
| ciliary disk | The darkly pigmented posterior zone of the ciliary body continuous with the retina at the ora serrata. Synonym: ciliary disk, ciliary ring, pars plana. Origin: Mod. L. (05 Mar 2000) |
| Placido da Costa's disk | <instrument> An instrument marked with lines or circles by means of which the corneal reflex can be observed. Synonym: Placido da Costa's disk. Origin: kerato-+ G. Skopeo, to examine (05 Mar 2000) |
| porous disk | <chemistry> A disk in a tube connecting two different solutions in a voltaic cell that allows ion flow without extensive mixing of the solutions, similar to a salt bridge. (09 Jan 1998) |
| hair disk | A richly innervated area of skin around a hair follicle, consisting of a thickened layer of epithelial cells in which ramify unmyelinated terminals of a single axon. (05 Mar 2000) |
| cuttlefish disk | A circle of paper or thin plastic coated with ground cuttlefish bone; used, when attached to a mandrel and rotated by a dental handpiece, for fine smoothing and finishing of dental materials and tooth. (05 Mar 2000) |
| H disk | <cell biology> The H band is an area within muscle tissue which is light when stained and consists only of myosin fibres (and no actin fibres). The H band is at the centre of each muscle sarcomere. (09 Oct 1997) |
| prolapsed disk | A condition that results in the abnormal protrusion (bulging), herniation or prolapse of a vertebral disc from its normal position in the vertebral column. The displaced disc may exert force on a nearby nerve root causing the typical neurologic symptoms of radiating pain (to an extremity), numbness, tingling and weakness. Recurrent episodes of severe back pain are common. Treatment includes non-steroidal anti-inflammatory drugs, corticosteroids and rest. More advanced cases may require surgical intervention (for example laminectomy, micro-disc surgery). (27 Sep 1997) |