470
UNIT THREE
TABLE
12.6
|
Layers of the Eye
Layer/Tunic
Posterior Portion
Function
Anterior Portion
Function
Outer layer
Sclera
Protection
Cornea
Light transmission and refraction
Middle layer
Choroid coat
Blood supply, pigment prevents reF
ection
Ciliary body, iris
Accommodation; controls light intensity
Inner layer
Retina
Photoreception, impulse transmission
None
Veins
Optic
disc
Artery
Fovea
centralis
Macula
lutea
(a)
(b)
FIGURE 12.34
The retina. (
a
) Major features of the retina. (
b
) Nerve ±
bers
leave the retina in the area of the optic disc (arrow) to form the optic nerve in
this magni±
ed view (53×).
Sclera
Choroid coat
Retinal pigment epithelium
Receptor cells
(rods and cones)
Bipolar neurons
Ganglion cells
Nerve fibers
FIGURE 12.33
Note the layers of cells and nerve ±
bers in this light micrograph of the retina (75×).
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