cone
[kōn] 1. a solid figure or body having a circular base and tapering to a point.
2. one of the conelike structures which, with the
rods, form the light-sensitive elements of the
retina; the cones make possible the perception of color. See also
eye and
vision. Called also
retinal cone.
3. in radiology, a conical or open-ended cylindrical structure formerly used as an aid in centering the radiation beam and as a guide to source-to-film distance. Cones were commonly attached to the x-ray tube prior to the use of the
collimator.
4. in
root canal therapy, a solid substance with a tapered form, usually made of gutta-percha or silver, fashioned to conform to the shape of a root canal.
ether cone a cone-shaped device used over the face in administration of ether for anesthesia.
gutta-percha cone in
root canal therapy, a plastic radiopaque cone made from gutta-percha and other ingredients, available in standard sizes according to the dimensions of root canal reamers and files; used to fill and seal the canal along with sealer cements. Called also
gutta-percha point.
cone of light the triangular reflection of light seen on the tympanic membrane.
pressure cone the area of compression exerted by a mass in the brain, as in transtentorial herniation.
retinal cone cone (def. 2).
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.