Sclera
233154
221823939
2008-06-26T07:30:12Z
74.236.198.223
removed inane babble.
{{Infobox Anatomy |
Name = {{PAGENAME}} |
Latin = |
GraySubject = 225 |
GrayPage = 1006 |
Image = Schematic diagram of the human eye en.svg |
Caption = Schematic diagram of the human eye. |
Image2 = |yuck
Caption2 = |
Width = 325 |
Precursor = |
System = |
Artery = [[anterior ciliary arteries]], [[long posterior ciliary arteries]], [[short posterior ciliary arteries]] |
Vein = |
Nerve = |
Lymph = |
MeshName = Sclera |
MeshNumber = A09.371.784 |
DorlandsPre = |
DorlandsSuf = |
}}
The '''sclera''', called the '''white''' or '''white of the eye''', is the opaque (usually white, though certain animals, such as horses and lizards, can have black sclera), fibrous, protective, outer layer of the [[eye]] containing [[collagen]] and [[elastic fiber]]s.<ref name="Cassin">Cassin, B. and Solomon, S. ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing Company, 1990.</ref> It is derived from the [[neural crest]]<ref>Hermann D. Schubert. ''Anatomy of the Orbit'' http://www.nyee.edu/pdf/schubert.pdf</ref>. In children, it is thinner and shows some of the underlying pigment, appearing slightly blue. In the elderly, however, fatty deposits on the sclera can make it appear slightly yellow.
The sclera forms the posterior five sixths of the connective tissue coat of the globe. It is continuous with the dura mater, and maintains the shape of the globe, offering resistance to internal and external forces, and provides an attachment for the extraocular muscle insertions. The thickness of the sclera varies from 1mm at the posterior pole to 0.3 mm just behind the rectus muscle insertions. The main parts of the eye also include the conjunctiva. This is a thin layer covering the sclera.
[[Image:Limbus.png|thumb|left|200px|Limbus is the border between cornea and sclera]]
It borders with the [[cornea]] by the [[corneal limbus]].
----
==Histology==
From outer to innermost, the three layers of the sclera are:
* Episclera
* Stroma
* Lamina fusca
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
To avoid confusion, the cornea, which is an outer continuation from the sclera, has 5 layers. The middle, thickest layer is also called the stroma. Lazic surgery to correct vision is usually done in this region of the cornea.
==Additional images==
<gallery>
Image:Gray875.png|Interior of anterior half of bulb of eye.
Image:Gray880.png|The terminal portion of the optic nerve and its entrance into the eyeball, in horizontal section.
Image:Gray1206.png|The interior of the posterior half of the left eyeball.
</gallery>
==References==
<div class="references-small">
<references/>
</div>
==External links==
* {{BUHistology|08008loa}}
* {{UMichAtlas|eye_1}} - "Sagittal Section Through the Eyeball"
{{eye-stub}}
{{Eye}}
{{Visual_system}}
{{Muscles of orbit}}
[[category:eye]]
[[bn:স্ক্লেরা]]
[[ca:Escleròtica]]
[[de:Sclera]]
[[es:Esclerótica]]
[[eu:Esklerotika]]
[[fr:Sclère]]
[[it:Sclera]]
[[lt:Odena]]
[[nl:Sclera]]
[[no:Sklera]]
[[pl:Twardówka]]
[[pt:Esclera]]
[[ru:Склера]]
[[sk:Očné bielko]]
[[fi:Kovakalvo]]
[[ur:صُلبہ]]
[[zh:巩膜]]