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Biological: Behavioural genetics · Evolutionary psychology · Neuroanatomy · Neurochemistry · Neuroendocrinology · Neuroscience · Psychoneuroimmunology · Physiological Psychology · Psychopharmacology (Index, Outline)
| Iris sphincter | ||
|---|---|---|
 | ||
| Iris, front view. (Muscle visible but not labeled.) | ||
| The upper half of a sagittal section through the front of the eyeball. ("Circular fibers" labeled near center.) | ||
| Latin | m. sphincter pupillae | |
| Gray's | subject #225 1013 | |
| Origin: | ||
| Insertion: | ||
| Artery: | ||
| Nerve: | short ciliary nerves | |
| Action: | constricts pupil | |
| Antagonist: | iris dilator muscle | |
| Dorlands/Elsevier | m_22/12550831 | |
The iris sphincter muscle (pupillary sphincter, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris.
It is found in vertebrates and some cephalopods.
In humans, it functions to constrict the pupil in bright light (pupillary reflex) or during accommodation.
It is controlled by parasympathetic fibers that originate from the Edinger-Westphal nucleus, travel along the oculomotor nerve (CN III), synapse in the ciliary ganglion, and then enter the eye via the short ciliary nerves.
Additional images[]
See also[]
External links[]
- Overview of function at tedmontgomery.com
- Slide at mscd.edu
- Dictionary at eMedicine sphincter+pupillae
scalp/eyelid: occipitofrontalis (occipitalis, frontalis) - orbicularis oculi - corrugator supercilii - depressor supercilii
extraocular: levator palpebrae superioris - superior tarsal - rectus (superior, inferior, medial, lateral) - oblique (superior, inferior) - intraocular: ciliary - iris dilator - iris sphincter
ear: auriculares - temporoparietalis - stapedius - tensor tympani
nose: procerus - nasalis (dilatator naris) - depressor septi nasi - levator labii superioris alaeque nasi
mouth: levator anguli oris/depressor anguli oris - levator labii superioris/depressor labii inferioris - zygomaticus (major, minor) - mentalis - buccinator - orbicularis oris - risorius
mastication: masseter - temporalis - pterygoid (lateral, medial)
tongue: extrinsic (genioglossus - hyoglossus - chondroglossus - styloglossus) intrinsic (superior longitudinal - inferior longitudinal - transversus - verticalis)
soft palate: levator veli palatini - tensor veli palatini - musculus uvulae - palatoglossus - palatopharyngeus
pharynx: pharyngeal constrictor (inferior, middle, superior) - stylopharyngeus - salpingopharyngeus
larynx: cricothyroid - posterior cricoarytenoid - lateral cricoarytenoid - arytenoid - thyroarytenoid
- hu:Musculus sphincter pupillae
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