Sphincter pupillae
Pupil is the central
small aperture situated within the iris of eye. The size of it control by two
muscles one is sphincter papillae and dilator papillae. So through pupil only
the appropriate amount of light enters the eye .
They are
involuntary muscle fibers of the iris, which arranged circularly.
It is only present in
papillary margin of iris. It is supplied by parasympathetic fibers from
Edinger-westphal nucleus of oculomotor nerve.
Function: constrictor of the pupil in response to bright light. Failure
of pupil to respond to light is an important clinical sign of the lack of nerve
or brain function.
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