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Iris: anatomy, location and function

The iris is the pigmented, contractile diaphragm in front of the lens that forms the pupil. It controls the pupil diameter and thus the light reaching the retina using the sphincter pupillae and dilator pupillae.

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Highlighted in the model: Iris. Click any part to read about it, or switch off “Highlight topic” to see the whole body. 3D data: BodyParts3D, © The Database Center for Life Science, CC BY 4.0; meshes simplified and recoloured. The model is an adult male.

Iris at a glance

What it is
The iris is the pigmented, contractile diaphragm in front of the lens that forms the pupil.
Location
It lies between the cornea and the lens, dividing the anterior and posterior chambers.
Function
It controls the pupil diameter and thus the light reaching the retina using the sphincter pupillae and dilator pupillae.
Body system
Eye & ear · paired (left and right)
FMA ID
FMA58237 (Foundational Model of Anatomy)

Key facts

  • Sphincter pupillae is parasympathetic (CN III); dilator pupillae is sympathetic.
  • Eye colour depends on iris pigment.
  • Its root attaches to the ciliary body, and the angle between it and the cornea is where aqueous humour drains.

Clinical relevance

Pupil abnormalities help localise nerve lesions.

Structures next to the iris

The nearest named structures in the 3D model, measured from the centre of each part:

References

  1. Foundational Model of Anatomy: Iris (FMA58237). EMBL-EBI Ontology Lookup Service.
  2. OpenStax. Anatomy and Physiology 2e, §14.1 Sensory Perception. Rice University, 2022.
  3. Mitsuhashi N. et al. (2009). BodyParts3D: 3D structure database for anatomical concepts. Nucleic Acids Research 37, D782–D785. Data © The Database Center for Life Science, CC BY 4.0.

Related anatomy

Explore the whole body in the interactive 3D human anatomy model, or browse the A–Z list of human structures.