Which muscle opens the pupil in darkness?

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Prepare for the Certified Paraoptometric Assistant (CPOA) Exam. Study with extensive flashcards and multiple choice questions with explanations. Enhance your skills and knowledge to succeed.

Multiple Choice

Which muscle opens the pupil in darkness?

Explanation:
In darkness, the pupil enlarges to let in more light, and this is done by the dilator pupillae, the radial muscle of the iris. When the sympathetic system activates this muscle, it contracts and pulls the iris outward, widening the pupil (mydriasis). The opposing sphincter pupillae is a circular muscle that constricts the pupil under parasympathetic control in bright light or for near vision, the ciliary muscle adjusts lens shape for focusing, and the iris itself is the tissue housing these muscles. So, the muscle that opens the pupil in darkness is the dilator pupillae.

In darkness, the pupil enlarges to let in more light, and this is done by the dilator pupillae, the radial muscle of the iris. When the sympathetic system activates this muscle, it contracts and pulls the iris outward, widening the pupil (mydriasis). The opposing sphincter pupillae is a circular muscle that constricts the pupil under parasympathetic control in bright light or for near vision, the ciliary muscle adjusts lens shape for focusing, and the iris itself is the tissue housing these muscles. So, the muscle that opens the pupil in darkness is the dilator pupillae.

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