HISTOLOGY OF EYE

EPITHELIUM Stratified squamous non keratinized Consist of 5-6 layer Active mitosis Turnover time for cells is 6-7 days Extremely sensitive to touch

BOWMANS MEMBRANE Consists of collagen fibers Acellular clear membrane lie under the epithelium Cannot be regenerated if destroyed Provides strength to cornea Acts as a barrier against spread of infections

CORNEAL STROMA Many layers of collagen bundles run parallel to each other and parallel to the surface of the cornea making the cornea transparent, Avascular structure Nuclei of fibroblasts 90% of corneal thickness

DESCEMENTS MEMBRANE Fine collagenous filaments 5-10 micrometer thick Regenerates quickly

ENDOTHELIUM Single layer of flat hexagonal cells with no mitosis Pumps water out Prevent corneal edema opacification Maintain corneal transparency

LENS Capsule Refractile and formed of type IV collagen Sub capsular epithelium Single layer of cuboidal epithelium present on anterior surface Lens fibers Highly differentiated cells.

LENS FIBERS Form the body of the lens. located deep to the subcapsular epithelium. Nucleated in the soft, outer cortex of the lens. As new lens fibers are added to the periphery of the cortex, lens fibers located deeper in the cortex loose their nuclei . Cytoplasm filled with crystalline proteins. These proteins are responsible for the transparency .

RETINA Innermost layer of eye ball Develops from double walled optic cup Outer layer forms pigment epithelium Inner layer forms neural retina

RETINA The retina is the site of sensory transduction The retina is nervous tissue composed of 6 major types of neurons and one special type of glial-like cell (the Muller cell)  The organization of the retina is based on a three neuron chain (photoreceptor cell to bipolar cell to ganglion cell)

MAJOR RETINAL CELLS RODS Thin elongated cells Composed of inner and outer segments 120 million photoreceptor cells called rods (responsible for peripheral and dim light vision) Contain rhodopsin

MAJOR RETINAL CELLS CONES Lesser in number than rods Responsible for providing central, bright light, fine detail, and color vision Contain visual pigment iodopsin

MAJOR RETINAL CELLS Horizontal cells - interconnect groups of photoreceptor cells Bipolar cells - interconnect photoreceptor cells with ganglion cells Amacrine cells interconnect groups of ganglion cells and bipolar cells Ganglion cells possess long axons that extend through the nerve fiber layer of the retina and then come together to form the optic nerve

LAYERS OF RETINA Pigment epithelium The layer of rods and cones External limiting membrane. The outer nuclear layer Outer plexiform layer Inner nuclear layer. The internal plexiform layer Ganglion cell layer. Layer of optic nerve fibers The internal limiting membrane

PIGMENT EPITHELIUM Consist of columnar cells Absorbs light Synthesizes melanin granules Vitamin A metabolism Cells have phagocytic properties

LAYER OF RODS AND CONES

EXTERNAL LIMITING MEMBRANE Not a true membrane Formed of row of zonula adherens between muller cells and rods and cones

OUTER NUCLEAR LAYER

OUTER PLEXIFORM LAYER Formed by the processes of photoreceptor cells and retinal neuronal cells that is horizontal, bipolar and amacrine cells

INNER NUCLEAR LAYER Consist of nuclei of bipolar, amacrine, horizontal and muller cells

INTERNAL PLEXIFORM LAYER Formed of complex intermingled nerve cell processes

GANGLION CELL LAYER Consist of cell bodies of large multipolar neurons

OPTIC NERVE LAYER Consist of axons of ganglion cells

INTERNAL L+-IMITING MEMBRANE