Zonule

Zonule of Zinn
Schematic diagram of the human eye. (Zonular fibers labeled at upper left.)
The upper half of a sagittal section through the front of the eyeball. (Zonule of Zinn visible near center.)
Latin zonula ciliaris
Gray's subject #226 1018

The zonule of Zinn (Zinn's membrane, ciliary zonule) (after Johann Gottfried Zinn) is a ring of fibrous strands connecting the ciliary body with the crystalline lens of the eye.

Development

The ciliary epithelial cells of the eye probably synthesize portions of the zonules.[1]

Anatomy

The zonule of Zinn is split into two layers: a thin layer, which lines the hyaloid fossa, and a thicker layer, which is a collection of zonular fibers. Together, the fibers are known as the suspensory ligament of the lens.[2] The zonules are about 1–2 μ in diameter.[3]

When colour granules are displaced from the Zonules of Zinn (by friction against the lens), the irises slowly fade. In some cases those colour granules clog the channels and lead to Glaucoma Pigmentosa.

The zonules are primary made of fibrillin, a connective tissue protein.[1] Mutations in the fibrillin gene lead to the condition Marfans Syndrome, and consequences include an increased risk of lens dislocation.[1]

Clinical appearance

The zonules of Zinn are difficult to visualize using a slit lamp, but may be seen with exceptional dilation of the pupil, or if a coloboma of the iris or a suluxation of the lens is present.[4] The number of zonules present in a person appears to decrease with age.[3] The zonules insert around the outer margin of the lens (equator), both anteriorly and posteriorly.[5]

Additional Images

References

External links

  • Diagram at unmc.edu
  • Diagram at eye-surgery-uk.com
  • Diagram and overview at webschoolsolutions.com
  • eMedicine Dictionary
  • 08011loa

This article incorporates text from a public domain edition of Gray's Anatomy.