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the eye

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by

sara tantawi

on 10 March 2015

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Transcript of the eye

factors responsible for corneal transparency
1.
The surface epithelium is non keratinized.
2.
The free nerve endings are unmyelinated.
3.
بRegular arrangement of lamellae of substantia propria.
4
. Cells, lamellae and matrix of substantia propria have the same refractive index.
5.
Cornea is avascular.
6.
Minimal hydration of the cornea.
the sclera
Lasik surgery
:
laser is used to change the corneal curvature to improve some visual abnormalities.
Injury of the anterior limiting membrane(bowman`s membrane result
in
corneal opacity
.
Corneal transplantation
:
usually succeeds brcause cornea is avavscolar.
Mcrovilli keep cornea (tear film) to avoid
corneal ulceration
.
Glaucoma :
the fluid pressure inside the eye rises because of slowed fluid drainage from the eye.
Keratoconus
: Keratoconus is a condition in which the cornea bulges outward like a cone, the cause of the condition is unknown, but genetics may play a role
structure of the eye ball
introduction
1. general structure of the eye
2. layers of the eye ball:
* external fibrous supporting layer ( cornea and sclera).
* middle vascular layer (iris, ciliary body and choroid).
* inner nervous layer (retina).
the eye
the cornea

1. nonkeratinized stratified squamous eithelium (5-6 layers):

a. basal layer : cibical-colamnur cells, high regenerative capacity.
b. intermediate layer : 3-4 layers, polyhedral cells, unmyelinated nerve endings.
c. top layer : squamous cells, apical microvilli.

2. anterior limiting membrane (bouman`s membrane):
non cellular, formed of collagen fibrils, thick for stability, cannot regenerate.

3. substantia propria:
main thickness, 60 layers of collagen bundles , keratocytes, proteoglycans.

4. posterior limiting membrane (descemet`s membrane):
non-cellular, basement membrane for endothelium.
5. endothelium:

single layer of simple squamous epithelium
responsible for:
- maintain the descemet`s membrane.
- keeps an optimum state of corneal hydration fo maximum
transparency.

Bnisuif university
Faculty of medicine
Histology department
set back, relax and enjoy our presentation
the transparent part.
formed of five layers:
layers of cornea
histology of cornea
- the obaque part
- changes at corneo-scleral junction (limbus) :
1.
at the junction, the conjuctival epihelium is non keratisied stratified squamous epithelium, concentrated stem cells.
2.
bowman`s membrane is replaced y subconjuctival C.T.
3
. collagen lamellae become irregular , canal of Schlemm.
4.
Decemet`s membrane and its simple endothelium are replaced with trabecular meshwork.
clinical applicatons:
Full transcript