Which muscle controls pupil size?

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Study for the History and Physical (Handamp;P) Exam 1. Prepare with flashcards and multiple choice questions, each question has hints and explanations. Get ready for your exam!

Multiple Choice

Which muscle controls pupil size?

Explanation:
Pupil size is controlled by muscles within the iris. The iris has two smooth muscles that adjust diameter: the sphincter pupillae, which constricts the pupil (miosis) in bright light or with parasympathetic activation, and the dilator pupillae, which widens the pupil (mydriasis) under sympathetic stimulation or in dim light. The ciliary muscle governs lens focusing, not pupil size. The retinal pigment epithelium and conjunctival muscles do not regulate pupil diameter. So the iris muscle is the structure that controls how large the pupil appears.

Pupil size is controlled by muscles within the iris. The iris has two smooth muscles that adjust diameter: the sphincter pupillae, which constricts the pupil (miosis) in bright light or with parasympathetic activation, and the dilator pupillae, which widens the pupil (mydriasis) under sympathetic stimulation or in dim light. The ciliary muscle governs lens focusing, not pupil size. The retinal pigment epithelium and conjunctival muscles do not regulate pupil diameter. So the iris muscle is the structure that controls how large the pupil appears.

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