Zonule of Zinn

Part of the eye

Zonule of Zinn
Anatomy of the anterior part of the human eye. "Suspensory ligaments" are labeled at left.
The upper half of a sagittal section through the front of the eyeball. (Zonule of Zinn visible near center.)
Details
Identifiers
Latin	zonula ciliaris
TA98	A15.2.05.015
TA2	6795
FMA	58838
Anatomical terminology [edit on Wikidata]

The zonule of Zinn (/ˈtsɪn/) (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.^[1] These fibers are sometimes collectively referred to as the suspensory ligaments of the lens, as they act like suspensory ligaments.

Development

The non-pigmented ciliary epithelial cells of the eye synthesize portions of the zonules.^[2]^[3]

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.^[4] The zonules are about 1–2 μm in diameter.^[5]

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.^[6]^[7]

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 primarily made of fibrillin, a connective tissue protein.^[2] Mutations in the fibrillin gene lead to the condition Marfan syndrome, and consequences include an increased risk of lens dislocation.^[2]

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 subluxation of the lens is present.^[8] The number of zonules present in a person appears to decrease with age.^[5] The zonules insert around the outer margin of the lens (equator), both anteriorly and posteriorly.^[9]

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

Structures of the eye labeled
This image shows another labeled view of the structures of the eye

References

This article incorporates text in the public domain from page 1018 of the 20th edition of Gray's Anatomy (1918)

^ Zinn, J (1755). Descriptio Anatomica Oculi Humani Iconibus Illustrata (Latin ed.). Gottingen: Viduam B. Abrami Vandenhoeck.
^ ^a ^b ^c Kaufman, Paul L.; Alm, Albert (2010). Adler's physiology of the eye (11th ed.). St. Louis, Mo: Mosby. pp. 145–146. ISBN 978-0-323-05714-1.
^ Shi, Yanrong; Tu, Yidong; De Maria, Alicia; Mecham, Robert P.; Bassnett, Steven (1 April 2013). "Development, Composition, and Structural Arrangements of the Ciliary Zonule of the Mouse". Investigative Ophthalmology & Visual Science. 54 (4): 2504–2515. doi:10.1167/iovs.13-11619. PMC 3621578. PMID 23493297.
^ "Vision - via the optic nerve (CN II)". Archived from the original on September 17, 2008. Retrieved January 12, 2008.^{[full citation needed]}
^ ^a ^b Bornfeld, Norbert; Spitznas, Manfred; Breipohl, Winrich; Bijvank, Gerhard J. (1974). "Scanning electron microscopy of the zonule of Zinn". Albrecht von Graefes Archiv für Klinische und Experimentelle Ophthalmologie. 192 (2): 117–29. doi:10.1007/BF00410698. PMID 4548321. S2CID 23592537.
^ Remington, Lee Ann (2012). Clinical anatomy and physiology of the visual system (3rd ed.). St. Louis: Elsevier/Butterworth-Heinemann. p. 97. ISBN 978-1437719260.
^ "2020–2021 BCSC Basic and Clinical Science Course™". www.aao.org.
^ McCulloch, C (1954). "The zonule of Zinn: Its origin, course, and insertion, and its relation to neighboring structures". Transactions of the American Ophthalmological Society. 52: 525–85. PMC 1312608. PMID 13274438.
^ Farnsworth, P. N.; Mauriello, J. A.; Burke-Gadomski, P; Kulyk, T; Cinotti, A. A. (1976). "Surface ultrastructure of the human lens capsule and zonular attachments". Investigative Ophthalmology. 15 (1): 36–40. PMID 1245377.

External links

Diagram at unmc.edu
Diagram at eye-surgery-uk.com
Diagram and overview at webschoolsolutions.com
Histology image: 08011loa – Histology Learning System at Boston University

Anatomy of the globe of the human eye

Fibrous tunic
(outer)

Sclera	Episcleral layer Schlemm's canal Trabecular meshwork
Cornea	Limbus layers Epithelium Bowman's Stroma Dua's layer Descemet's Endothelium

Uvea / vascular
tunic (middle)

Choroid	Capillary lamina of choroid Bruch's membrane Sattler's layer
Ciliary body	Ciliary processes Ciliary muscle Pars plicata Pars plana
Iris	Stroma Pupil Iris dilator muscle Iris sphincter muscle

Retina (inner)

Layers	Inner limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Layer of rods and cones Retinal pigment epithelium
Cells	Photoreceptor cells (Cone cell, Rod cell) → (Horizontal cell) → Bipolar cell → (Amacrine cell) → Retina ganglion cell (Midget cell, Parasol cell, Bistratified cell, Giant retina ganglion cells, Photosensitive ganglion cell) → Diencephalon: P cell, M cell, K cell, Muller glia
Other	Macula Perifoveal area Parafoveal area Fovea Foveal avascular zone Foveola Optic disc Optic cup Ora serrata

Anatomical regions
of the eye

Anterior segment	Adnexa (Eyebrow, Eyelid, Conjunctiva, Lacrimal system, Orbit) Fibrous tunic Anterior chamber Aqueous humour Iris Posterior chamber Ciliary body Lens Capsule of lens Zonule of Zinn
Posterior segment	Vitreous chamber Vitreous body Retina Choroid