Cornea - anterior 1/6th. An avascular disk consisting of five layers.
Anterior epithelium - thin nonkeratinized stratified squamous, with many free nerve endings.
Bowmans membrane - is a cell-free, thich basement menbrane composed of ground substance and reticular fibers.
The Stroma forms the cornea’s core and 90% of its thickness. Consists of many layers of collagen bundles.
Tunica Fibrosa
Cornea - anterior 1/6th. An avascular disk consisting of five layers.
Descemet’s membrane - a thick basement membrane differing from Bowman’s membrane in position and composition. Has elastin, but no elastic fibers. Its network of atypical collagen fibers is decorated with granules.
Corneal endothelium - a simple cuboidal epithelium lining the cornea’s internal surface.
Tunica Fibrosa
Sclera: an opaque white CT covering the posterior 5/6ths of the eyeball.
It is anchored in the orbit by dense CT of Tenon’s capsule.
It has three layers:
Episclera - outermost fibroelastic tissue.
Substantia propria - a dense mat of collagen bundles and fibroblasts forming the thick middle layer where the ocular muscles insert.
Lamina fusca - a loose CT layer containinf elastic fibers and melanocytes. It is separated from the choriod by the narrow perichoroidal space.
Choroid
Lies between the sclera and the retina’s pigmented layer and has four layers.
suprachoroidal lamina similar to the sclera’s lamina fusca.
vascular lamina - loose CT with many whorlike veins.
choriocapillary layer - layer of fenestrated sinusiods in loose CT.
Bruch’s membrane - inner layer of basement menbrane; is the basement membrane of the pigmented retina.
Ciliary Body
Extends from the choroid as a ringlike triangular thickening at the level of the lens.
Same layers as choroid minus the choriocapillaris.
Ciliary processes - irregular epithelium covered CT outgrowths of ciliary body towards the lens. Serve to anchor the lens via lens fibers and secretes aqueous humor.
Ciliary muscles - 3 groups of smooth muscle bundles that serve to focus the lens.
Iris
Controls amount of light reaching retina and gives color to the eye.
Projects as a flat ring from the ciliary body anterior to the lens.
The anterior surface is rough with pigmented cells and fibroblasts.
The stroma is a poorly vascularized CT.
The vascular stratum has many blood vessels.
The posterior surface is smooth, heavily pigmented, and continuous with the epithelium covering the ciliary body.
Two muscle layers - the circular sphincter pupillae and the projecting dilator pupillae.
Retina
Derived from the evagination of the diencephalon. Consists of two layers.
Pigmented retina - a melenin-rich simple cuboidal epithelium that rests on Bruch’e membrane. The cells many apical microvilli embrace the outer segments of the rods and cones in the neural retina. This layer is crucial to vision by absorbing light that has passed through the photosensitive layer, ensuring that light stimulated the rods and cones only on its first pass.
Retina
Neural retina - a highly organized sensitive photoreceptor that consists of ten distinguishable layers. Only three of which consist of retinal neurons.
Layer of Rods and Cones - contains the outer and inner segments of photoreceptor cells.
External (or outer) limiting layer - the apical boundary of Muller’s calls.
Outer nuclear layer - contains the cell bodies (nuclei) of retinal rods and cones.
Retina
Outer plexiform layer - contains processes of retinal rods and cones and processes of horizontal, amacrine, and bipolar cells that connect to them.
Inner nuclear layer - contains cell bodies of horizontal, amacrine, bipolar, and Muller’s cells.
Inner plexiform layer - contains the processes of horizontal, amacrine, and bipolar cells and processes of ganglion cells that connect to them.
Ganglion cell layer - contains the cell bodies of the ganglion cells.
Layer of optic nerve fibers - processes of the ganglion cells leading from retina to the brain.
Retina
Internal (inner) limiting membrane - composed of the basal lamina of Muller’s cells.
Retina
Fovea Centralis - directly opposite the center of the lens, it lies in the center of a deprision of the retina called the macula lutea. It has the greatest concentration of cones and has the greatest visual acuity.
Optic disk - blind spot; the optic disk is the site where the ganglion cell axons converge and exit the eye to form the optic nerve. It lacks photoreceptor cells.
Retinal vessels enter and exit the eye through the optic disk and branch over the retina’s internal surface.
Lens
A transparent, elastic, biconvex structure of epithelial origin. It has no blood or nerve supply, but is nurished by aqueous humor. Consists of three components.
Lens capsule - an elastic basal lamina that covers the lens and prevents wandering cells from penetrating it. Consist of type III and IV collagen embedded in a GAG-rich matrix.
Subcapsular epithelium - a low cuboidal epithelium increases to columnar near the center of the lens, where cell division occurs. It forms the lens fibers.
Lens
Lens fibers - narrow, hexagonal, specialized epithelial cells that make up most of the lens. During differentiation, they lose their nuclei, fill with proteins called crystallins, and develop a variety of plasma membrane specializations including junctional complexes and ridgelike processes.
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