Iris dilator muscle

Iris dilator muscle
Iris dilator muscle
Gray878.png
Iris, front view. (Muscle visible but not labeled.)
Gray883.png
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[1]
Insertion    inner margins of iris[1]
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[2] of the eye, running radially in the iris and therefore fit as a dilator. It has its origin from the anterior epithelium.[3] It is innervated by the sympathetic system, which acts by releasing noradrenaline, which acts on α1-receptors.[4] 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.

Contents

Additional images

See also

References

  1. ^ 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>.
  2. ^ jneurosci.org Muscarinic and Nicotinic Synaptic Activation of the Developing..
  3. ^ "eye, human." Encyclopædia Britannica. Encyclopaedia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.
  4. ^ Rang, H. P. (2003). Pharmacology. Edinburgh: Churchill Livingstone. ISBN 0-443-07145-4.  Page 163

External links



Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • 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

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

  • dilator muscle — ▪ anatomy       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,… …   Universalium

  • Iris (anatomy) — Iris The iris is the blue area. The other structures visible are the pupil center and the white sclera surrounding the iris. The overlying cornea is pictured, but not visible, as it is transparent …   Wikipedia

  • 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

  • Iris muscle — may refer to: *Iris sphincter muscle *Iris dilator muscle …   Wikipedia

  • Ciliary muscle — The choroid and iris. (Ciliary muscle is labeled near top.) Latin musculus ciliaris Gray s …   Wikipedia

  • 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

  • Intraoperative floppy iris syndrome — (IFIS) is a complication that may occur during cataract extraction in certain patients. This syndrome is characterized by a flaccid iris which billows in response to ordinary intraocular fluid currents, a propensity for this floppy iris to… …   Wikipedia

  • Iris — The iris is the circular, colored curtain of the eye. Its opening forms the pupil. The iris helps regulate the amount of light that enters the eye. The eye has a number of other key components. These include the cornea, pupil, lens, retina,… …   Medical dictionary

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”