Iris sphincter muscle - Wikipedia
The iris sphincter muscle (pupillary sphincter, pupillary constrictor, circular muscle of iris, circular fibers) is a muscle in the part of the eye called the iris. It encircles the pupil of the iris, appropriate to its function as a constrictor of the pupil.
Anatomy, Head and Neck: Eye Iris Sphincter Muscle
2023年7月30日 · The sphincter muscle fibers are located near the pupillary margin and are slightly anterior to the pigmented epithelium of the iris. It encircles the pupil of the iris and functions to constrict the pupil in bright light via the pupillary light reflex or during accommodation.
Direct retino-iridal projections and intrinsic iris contraction …
2024年8月14日 · Reduction rates were in general larger than those observed in intact eyes, most likely because the iris sphincter muscle must overcome less resistance and can thus achieve a larger...
Iris Sphincter Muscle - an overview | ScienceDirect Topics
The sympathetic regulation of the iris dilator muscle is mainly driven by α 1B-adrenoceptors, which contribute to the contraction of this muscle. This role has been demonstrated by means of selective antagonists that clearly abolish transmural contraction of the iris.
Sphincter pupillae: Origin, insertion, innervation,action - Kenhub
2023年11月3日 · Iris is a part of the eyeball that serves the regulation of the amount of light that reaches the retina, as it features an opening called the pupil through which the light can pass through. The diameter of the pupil is dynamic and it is regulated by a pair of antagonistic muscles found in the iris; the sphincter pupillae and the dilator pupillae.
Autonomic control of the eye and the iris
The iris controls the entrance of light towards the retina by adjusting the diameter of the pupil. This prerequisite for proper vision is mediated by iris muscles, innervated by autonomic nerves in all vertebrates from elasmobranchs to human, although significant differences between classes and species have been observed.
Iris | Eye, Structure, Anatomy, & Function | Britannica
2024年11月15日 · The iris consists of two sheets of smooth muscle with contrary actions—dilation (expansion) and contraction (constriction). These muscles control the size of the pupil and thus determine how much light reaches the sensory tissue of the retina.
The Anatomy of the Eye: Understanding the Iris Sphincter Muscle
2024年7月7日 · The iris sphincter muscle is a crucial component of the eye responsible for controlling the size of the pupil. Structurally, the iris sphincter muscle is a ring of smooth muscle fibers that encircle the pupil, and its function is to constrict the pupil in bright light and dilate it …
Contribution of Different Anatomical and Physiologic Factors to Iris ...
2013年4月26日 · Contraction of the dilator muscle, located in the extreme posterior of the iris, tends to curl the iris and bow it to the anterior, consequently narrowing the angle.
Functional innervation and contractile properties of the human iris ...
1988年6月1日 · In the human iris sphincter muscle, electrical field stimulation evoked a twitch contraction which was sensitive to TTX or atropine, thereby indicating that this muscle receives cholinergic excitatory innervation.