Challenge A Anatomy Practice Test

Which term refers to the black hole in the center of the iris that controls the amount of light entering the eye?

Pupil Retina Sclera Vitreous humor

Correct Answer:

Pupil

Explanation:

The opening in the center of the iris that controls how much light enters the eye is called the pupil. It acts as the entryway for light, and its size is adjusted by the iris muscles: in bright light the pupil constricts to reduce light entry, and in dim light it dilates to let in more light. The dark appearance comes from the fact that light that passes through is not reflected back, so the opening looks black. The other structures have different roles: the retina is the light-sensitive tissue at the back of the eye; the sclera is the tough white outer coating; and the vitreous humor is the clear gel filling the main chamber.

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