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the iris has two parts. list them and their nerve supplz and their actions.
• Circularly-arranged fibres of sphincter pupillae arranged around the margin of the pupil close it in the presence of bright light and during accommodation. This occurs under
parasympathetic control from the oculomotor nerve via the ciliary ganglion and short ciliary nerves.
• Radially-arranged fibres of dilator pupillae, forming a thin sheet close to the posterior surface of the iris, open the pupil in the presence of light of low intensity or in the presence of excessive sympathetic activity (such as occurs in fright).
This occurs under sympathetic control via the long ciliary nerves.
parasympathetic control from the oculomotor nerve via the ciliary ganglion and short ciliary nerves.
• Radially-arranged fibres of dilator pupillae, forming a thin sheet close to the posterior surface of the iris, open the pupil in the presence of light of low intensity or in the presence of excessive sympathetic activity (such as occurs in fright).
This occurs under sympathetic control via the long ciliary nerves.
