The zonule of Zinn () (Zinn's membrane, ciliary zonule) (after

Johann Gottfried Zinn Johann Gottfried Zinn (; December 4, 1727 – April 6, 1759) was a German Anatomy, anatomist and botanist and was a member of the Prussian Academy of Sciences, Berlin Academy. Biography Johann Gottfried Zinn was born in Schwabach. Considerin ...

) is a ring of fibrous strands forming a zonule (little band) that connects the

ciliary body The ciliary body is a part of the eye that includes the ciliary muscle, which controls the shape of the lens, and the ciliary epithelium, which produces the aqueous humor. The aqueous humor is produced in the non-pigmented portion of the ciliary ...

with the crystalline

lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...

of the

eye An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

. The Zonular fibers are viscoelastic cables, although their component microfibrils are stiff structures. These fibers are sometimes collectively referred to as the suspensory ligaments of the lens, as they act like suspensory

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

Development

The non-pigmented ciliary epithelial cells of the eye synthesize portions of the zonules.

Anatomy

The zonule of Zinn is split into two layers: a thin layer, which lies near 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. The zonules are about 1–2 μm in diameter. The zonules attach to the lens capsule 2 mm anterior and 1 mm posterior to the equator, and arise of the ciliary epithelium from the pars plana region as well as from the valleys between the ciliary processes in the pars plicata. 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 Glaucoma is a group of eye diseases that can lead to damage of the optic nerve. The optic nerve transmits visual information from the eye to the brain. Glaucoma may cause vision loss if left untreated. It has been called the "silent thief of ...

pigmentosa. The zonules are primarily made of fibrillin, a connective tissue protein. Mutations in the fibrillin gene lead to the condition

Marfan syndrome Marfan syndrome (MFS) is a multi-systemic genetic disorder that affects the connective tissue. Those with the condition tend to be tall and thin, with dolichostenomelia, long arms, legs, Arachnodactyly, fingers, and toes. They also typically ha ...

, and consequences include an increased risk of lens dislocation.

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 A coloboma (from the Greek , meaning "defect") is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is ...

of the iris or a subluxation of the lens is present. The number of zonules present in a person appears to decrease with age. The zonules insert around the outer margin of the lens (equator), both anteriorly and posteriorly.

Function

Securing the lens to the optical axis and transferring forces from the ciliary muscle in accommodation. When colour granules are displaced from the zonules of Zinn, caused by friction of the lens, the iris can slowly fade. These colour granules can clog the channels and lead to glaucoma pigmentosa.

Additional images

File:Three Main Layers of the Eye.png, Structures of the eye labeled File:Three Internal chambers of the Eye.svg, Another labeled view of the structures of the eye

References

External links

Diagram at unmc.edu

Diagram at eye-surgery-uk.com

* {{DEFAULTSORT:Zonule Of Zinn Human eye anatomy Ligaments Anatomy named for one who described it