zonule of Zinn

(redirected from Zonular fibres)


a small zone.
ciliary zonule (zonule of Zinn) a series of fibers connecting the ciliary body and lens of the eye, holding the lens in place.
Ciliary zonule. The system of suspensory ligaments holding the lens in position. From Dorland's, 2000.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

Zinn, Johann

(zin, tsin)
Johann Gottfried Zinn, Ger. anatomist and botanist, 1727–1759.

annulus of Zinn

A ring of fibrous tissue behind the eye that surrounds the optic nerve and the ophthalmic artery and vein. It consists of the origins of five of the extraocular muscles: the superior oblique, and the inferior, lateral, medial, and superior rectus muscles.
Synonym: annular tendon

tendon of Zinn

The portion of the fibrous ring (annulus tendineus communis) from which the inferior rectus muscle of the eye originates.

zonule of Zinn

Ciliary zonule.


(zon'ul?) [ zonula]
1. A small band or area. Synonym: zonula
2. The ciliary zonule.

ciliary zonule

The suspensory ligament of the crystalline lens. Synonym: zonula ciliaris; zonule of Zinn

zonule of Zinn

See: Zinn, Johann
Medical Dictionary, © 2009 Farlex and Partners

Zinn, zonule of 

A series of fibres passing from the ciliary body to the capsule of the lens at or near its equator, holding the lens in position and enabling the ciliary muscles to act upon it. The lens and zonule form a diaphragm that divides the eye into a small anterior area, which contains aqueous humour, and a larger posterior area, which contains vitreous humour. The zonule forms a ring that is roughly triangular in a meridional section. It is made up of fibres that are transparent and straight for the most part. The tension of these fibres varies with the state of contraction of the ciliary muscle and thus affects the convexity of the lens. The zonule of Zinn is made up of many non-cellular fibres, the fibrils of which consist of a cysteine-rich microfibrillar component of the elastic system, fibrillin. The fibres have been classified as follows: (1) The hyaloid zonule (orbiculo-posterior capsular fibres) which originate from the pars plana of the ciliary body and insert into the capsule just posterior to the equator at the edge of the patellar fossa. (2) The anterior zonule (orbiculo-anterior capsular fibres or anterior zonular sheet), which originate from the pars plana of the ciliary body and insert into the capsule just anterior to the equator. These are the strongest and thickest of the zonular fibres. (3) The posterior zonule (cilio-posterior capsular fibres or posterior zonular sheet), which originate from the pars plicata of the ciliary body and insert into the lens capsule posterior to the equator. These are the most numerous. (4) The equatorial zonule (cilio-equatorial fibres) which originate from the pars plicata of the ciliary body and insert into the lens capsule at the equator. Syn. suspensory apparatus of the lens; suspensory ligament; zonular fibres. See Hannover's canal; canal of Petit; ciliary processes; ora serrata.
Millodot: Dictionary of Optometry and Visual Science, 7th edition. © 2009 Butterworth-Heinemann
References in periodicals archive ?
(2) Although the lenticular theories propose age-related changes to the lens, capsule, and zonular fibres, the extralenticular mechanism includes ciliary muscle dysfunction, loss of elasticity in the posterior zonular fibres, and even decreased resistance of the vitreous against the lens capsule.
(28) Myopia may result from degeneration of zonular fibres, resulting in a release of zonular tension, which allows spherical deformation of the lens (spherophakia).
(1,2,3) The ciliary muscle was discovered in the middle of the 19th century and in 1853, Hermann von Helmholtz, published "A Theory Of Accommodation." He observed that for focusing on near objects, the contraction of the ciliary muscle allows a relaxation of the zonular fibres and consequently, a bulging of the crystalline lens.