01 / Location & anatomical relationships
In the center of the iris, at the front of the eye.
02 / Structure & organization
The pupil is a variable aperture within the iris. Light passes through it toward the lens and retina. Changes in its diameter result from iris-muscle activity rather than contraction of the opening itself.
03 / Function
It looks dark because light enters the eye through it.
04 / Mechanism
Light passes through this opening toward the lens and retina. The iris muscles make it wider or narrower. Both pupils normally respond when lighting changes, as the eyes and nervous system work together.
Part of a bigger picture
The pupil belongs in our brain & senses collection. Explore the nearby parts to see how this area of the body fits together.
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Connect structure with function
The pupillary light response involves sensory input through the optic nerve and parasympathetic motor output associated with the oculomotor nerve. Both pupils normally participate in this response.
Check your understanding
Locate the pupil in relation to its neighbors. Explain how the structural features described above support its function, then distinguish it from a nearby structure with a different role.
Keep learning
Continue with OpenStax Anatomy and Physiology for system-level study. This atlas is educational and has not undergone independent medical peer review.