dilator muscle

      any of the muscles (muscle) that widen a body part. In humans, the dilator muscle of the iris contains fibres that extend radially through the iris of the eye (eye, human) and involuntarily contract as available light decreases, thus dilating the pupil. Pupillary dilation is controlled primarily by the sympathetic nervous system (nervous system, human). Interruption of the innervation of the dilator muscle can cause an abnormally small pupil, a condition seen as part of Horner syndrome. Traumatic rupture of iris muscles can cause an irregularly shaped pupil. Dilator muscles can also be found in other parts of the body such as the nose, where the dilator naris muscle aids in widening the nostrils. Compare sphincter muscle.

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Universalium. 2010.

Look at other dictionaries:

  • dilator muscle — musculus dilatator …   Medical dictionary

  • dilator muscle of pupil — dilator pupillae muscle musculus dilatator pupillae …   Medical dictionary

  • Iris dilator muscle — Iris, front view. (Muscle visible but not labeled.) …   Wikipedia

  • iris dilator muscle — noun A muscle of the eye, serving to dilate the iris. Syn: pupil dilator muscle, pupillary dilator, radial muscle of iris …   Wiktionary

  • Dilator — is a medical term with a number of uses, including: A surgical instrument or medical implement used to induce dilation, that is, to expand an opening or passage such as the cervix, urethra, esophagus, or vaginal introitus. A pharmacological… …   Wikipedia

  • dilator naris muscle — dilator muscle of naris pars alaris musculi nasalis …   Medical dictionary

  • muscle — muscleless, adj. muscly, adj. /mus euhl/, n., v., muscled, muscling, adj. n. 1. a tissue composed of cells or fibers, the contraction of which produces movement in the body. 2. an organ, composed of muscle tissue, that contracts to produce a… …   Universalium

  • dilator — noun 1》 (also dilator muscle) Anatomy a muscle whose contraction dilates an organ or aperture, such as the pupil of the eye. 2》 a surgical instrument for dilating a tube or cavity in the body. 3》 a vasodilatory drug …   English new terms dictionary

  • Muscle — is the tissue of the body which primarily functions as a source of power. There are three types of muscle in the body. Muscle which is responsible for moving extremities and external areas of the body is called "skeletal muscle." Heart… …   Medical dictionary

  • Dilator naris muscle — Muscles of the head, face, and neck. Latin pars alaris musculi nasalis Gray s …   Wikipedia

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