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

Johann Gottfried Zinn Johann Gottfried Zinn () (December 6, 1727 – April 6, 1759) was a German anatomist and botanist and was a member of the Berlin Academy. Biography Johann Gottfried Zinn was born in Schwabach. Considering his short life span, Zinn made a grea ...

) is a ring of fibrous strands forming a

zonule The zonule of Zinn () (Zinn's membrane, ciliary zonule) (after Johann Gottfried Zinn) is a ring of fibrous strands forming a zonule (little band) that connects the ciliary body with the crystalline lens of the eye. These fibers are sometimes colle ...

(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 ciliar ...

with the crystalline

lens A lens is a transmissive optical device which 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. These fibers are sometimes collectively referred to as the suspensory ligaments of the lens, as they act like suspensory

ligament A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...

Development

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

Anatomy

The zonule of Zinn is split into two layers: a thin layer, which lines the

hyaloid fossa The hyaloid fossa is a depression on the anterior surface of the vitreous body The vitreous body (''vitreous'' meaning "glass-like"; , ) is the clear gel that fills the space between the lens and the retina of the eyeball (the vitreous chamber) ...

, 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 result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for fluid within the eye rem ...

pigmentosa. The zonules are primarily made of

fibrillin Fibrillin is a glycoprotein, which is essential for the formation of elastic fibers found in connective tissue. Fibrillin is secreted into the extracellular matrix by fibroblasts and becomes incorporated into the insoluble microfibrils, which ...

, 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 long arms, legs, fingers, and toes. They also typically have exceptionally flexible joints a ...

, 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 pres ...

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, This image shows 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