Iris dilator muscle
Iris dilator muscle Iris, front view. (Muscle visible but not labeled.) The upper half of a sagittal section through the front of the eyeball. (Iris dilator muscle is NOT labeled and not to be confused with "Radiating fibers" labeled near center, which are part of the ciliary muscle.) Latin musculus dilatator pupillae Gray's subject #225 1013 Origin outer margins of iris Insertion inner margins of iris Artery Nerve Long ciliary nerves (sympathetics) Actions dilates pupil Antagonist iris sphincter muscle
The iris dilator muscle (pupil dilator muscle, pupillary dilator, radial muscle of iris, radiating fibers), is a smooth muscle of the eye, running radially in the iris and therefore fit as a dilator. It has its origin from the anterior epithelium. It is innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors. Thus, when presented with a threatening stimuli that activates the fight-or-flight response, this innervation contracts the muscle and dilates the iris, thus temporarily letting more light reach the retina.
- ^ a b Gest, Thomas R; Burkel, William E. "Anatomy Tables - Eye." Medical Gross Anatomy. 2000. University of Michigan Medical School. 5 Jan. 2010 <http://anatomy.med.umich.edu/nervous_system/eye_tables.html>.
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- Description of function at tedmontgomery.com
- Slide at mscd.edu
- dilator+pupillae+muscle at eMedicine Dictionary
- Histology at BU 08010loa
Sensory system – visual system – globe of eye (TA A15.2.1–6, TH 3.11.08.0-5, GA 10.1005) Fibrous tunic (outer) Uvea/vascular tunic (middle) Retina (inner)LayersCellsOther Anterior segment Posterior segment Other
Sensory system: Visual system and eye movement pathways Visual perception Muscles of orbitTrackingHorizontal gazeVertical gaze Pupillary reflexPupillary dilation Circadian rhythm
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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
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