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The expression dilator pupillae muscle, as used in the list of English equivalents of the Terminologia Anatomica, is actually partly Latin, i.e. dilator pupillae, with pupillae (=of the pupil [13]), a noun in the genitive case modifying dilator, a noun in the nominative case, and partly English, i.e. muscle.
The pupillary sphincter muscle and pupillary dilator muscle control the iris to adjust the size of the pupil to adjust how much light enters into the eye. The pupillary dilator muscle increases the pupillary diameter and it is arranged radially, but the pupillary sphincter muscle is responsible for the constriction of the pupil's diameter and ...
The pupil constricts when the iris sphincter muscle is stimulated and contracts. In humans, it functions to constrict the pupil in bright light (pupillary light reflex) or during accommodation. [citation needed] In lower animals, the muscle cells themselves are photosensitive causing iris action without brain input. [5]
The iris consists of two layers: the front pigmented fibrovascular layer known as a stroma and, behind the stroma, pigmented epithelial cells.. The stroma is connected to a sphincter muscle (sphincter pupillae), which contracts the pupil in a circular motion, and a set of dilator muscles (dilator pupillae), which pull the iris radially to enlarge the pupil, pulling it in folds.
Some humans have the ability to exert direct and voluntary control over their iris sphincter muscles and dilator muscles, granting them the ability to dilate and constrict their pupils on command, regardless of lighting condition and/or eye accommodation state. [15] However, this ability is very rare, and its potential use or advantages are ...
Iris (anatomy) Iris dilator muscle; Iris sphincter muscle; Layer of rods and cones; Lens (vertebrate anatomy) Macula; Mammalian eye; Müller glia; Night vision; Optic cup (anatomical) Optic disc; Optic pit; Optics; Ora serrata; Outer nuclear layer; Outer plexiform layer; Pars plana; Photoreceptor cell; Posterior chamber of eyeball; Posterior ...
There are two types of muscle that control the size of the iris: the iris sphincter, composed of circularly arranged muscle fibers, and the iris dilator, composed of radially arranged muscle fibers. The sphincter is controlled by nerves of the parasympathetic nervous system, and the dilator by the sympathetic nervous system.
Structure of the iris and surrounding parts showing the stroma of iris (stroma iridis). The stroma connects to a sphincter muscle ( sphincter pupillae ), which contracts the pupil in a circular motion, and a set of dilator muscles ( dilator pupillae ) which pull the iris radially to enlarge the pupil, pulling it in folds.