| optic disk | The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve. Because the retina at the optic disk has no photoreceptors there is a corresponding blind spot in the visual field. (12 Dec 1998) |
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| optic disk drusen | Hyaline bodies occurring in the intra-ocular portion of the optic nerve. They are distinguished from retinal drusen, which lie beneath the retinal pigment epithelium. This disorder is differentiated also from papilledema by the absence of dilated retinal vessels. (12 Dec 1998) |
| 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) |
| temporomandibular articular 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) |
| temporomandibular joint disk | A plate of fibrous tissue that divides the temporomandibular joint into an upper and lower cavity. The disk is attached to the articular capsule and moves forward with the condyle in free opening and protrusion. (boucher's clinical dental terminology, 4th ed, p92) (12 Dec 1998) |
| embryonic 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) |
| transverse disk | One of the dark transverse bands seen on examining a striated muscular fibre under the microscope. (05 Mar 2000) |
| triangular disk of wrist | 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) |
| Z disk | <cell biology> The line formed where actin filaments attach between two sarcomeres. (11 May 1997) |
| Lagrange disk | <microscopy> The exit pupil of the microscope, also called exit pupil, eyepoint and Ramsden circle or disk. (05 Aug 1998) |
| lumbar disk removal | A surgical procedure which is designed to relieve pressure on the spinal cord or nerve root that is being caused by a slipped or herniated disk in the lumbar spine. This procedure is also used in the treatment of spinal stenosis. This procedure includes removal of a portion of the bone comprising a vertebra. Recovery is generally 7-10 days. An alternative to this is a micro-disc surgery. (27 Sep 1997) |
| abnormal cleavage of cardiac valve | Congenital malformation of a valve leaflet with a defect extending from the free margin. (05 Mar 2000) |
| Amussat's valve | A series of crescentic folds of mucous membrane in the upper part of the cystic duct, arranged in a somewhat spiral manner. Synonym: plica spiralis ductus cystici, Amussat's valve, Heister's valve, spiral valve of cystic duct, valvula spiralis. (05 Mar 2000) |
| anterior cusp of atrioventricular valve | The anterior leaflet or valvule of either the tricuspid or mitral valves. Synonym: cuspis anterior valvae atrioventricularis dextrae/sinistrae. (05 Mar 2000) |
| anterior urethral valve | A crescentic horizontal fold in the proximal spongy urethra. (05 Mar 2000) |