WEEK 1: Histology of the eye Flashcards
State the 2 layers of the outer layer of the eye.
State the 2 parts of the retina.
State the 3 chambers of the eye.
Outer layer
*Sclera
*Cornea
Choroid
Retina has parts
*Neural Retina
*Pigmented epithelia
Lens
Chambers
Aqueous chambers – divided into
-Anterior (btn cornea and iris)
-Posterior (btn iris, ciliary body and lens)
-Vitreous chamber (behind lens)
Describe the histological layers of the eye.
The eyeball consists of three principal layers.
The outer layer, or sclera, consists of dense fibrous connective tissue.
The sclera is “white” of the eye.
The sclera is continuous with the transparent substantia propria of the cornea.
The exposed front surface of the eye, including the cornea, is also covered by a thin, non-keratinized stratified squamous epithelium.
The next layer, or choroid, consists of heavily pigmented loose connective tissue, including many melanocytes.
The choroid is normally not visible behind the “white” of the sclera.
The choroid is continuous with the iris; together the choroid and iris are called the uvea.
A hole in this layer, the pupil, allows light to pass through.
The inner layer, or retina, includes two portions.
The neural retina is the photoreceptive, imaging-processing tissue.
The pigmented epithelium lies behind the neural retina; it also extends forward to line the hidden side of the iris.
The lens is a specialized epithelial structure, suspended behind the pupil.
The anterior chamber, a space filled with aqueous humor, lies between the iris and the cornea.
The posterior chamber lies behind the iris.
Describe the cornea.
What epithelium is found in the cornea?
The cornea consists of a thin surface epithelium (non-keratinized stratified squamous) overlying a layer of dense fibrous connective tissue, called substantia propria.
The cornea is transparent.
Lacks blood vessels.
Describe the iris.
The iris is a rather simple opaque ring surrounding and controlling the diameter of its central aperture – the pupil.
Histological features.
The visible surface of the iris consists of loose connective tissue and includes blood vessels.
Trabecular meshwork of collagen fibers. Light is absorption of light by melanin granules in scattered melanocytes.
Eye color result the distribution and density of melanocytes and trabecular meshwork.
The posterior surface of the iris is an intensely pigmented extension of the embryological optic cup (the same tissue which forms the retina and the pigmented epithelium). This tissue continues as the ciliary processes around the perimeter of the iris.
Describe the lens.
The lens is basically two layers of epithelium
In the front is a simple cuboidal epithelium
Behind is an extremely exaggerated simple columnar epithelium;
Each of the columnar cells extends across the entire thickness of the lens and constitutes a lens fiber, packed with lens protein
The green line at the top of the image (above the nerve fiber layer) is the site of the inner limiting membrane, a basal lamina separating nervous tissue of the retina from connective tissue of the vitreous humor.
The layer of nerve fibers contains axons from ganglion cells which travel across the retina to the optic nerve and hence past the optic chiasm into the optic tract and into lateral geniculate nucleus of the thalamus.
The ganglion cell layer contains the cell bodies of ganglion cells, the cells whose axons project to the brain.
The inner plexiform layer contains dendrites of ganglion cells synapsing with axons of bipolar cells.
The inner nuclear layer contains the cell bodies of bipolar cells
The outer plexiform layer contains dendrites of bipolar cells synapsing with axons of photoreceptor cells.
The outer nuclear layer contains the cell bodies of receptor cells.
The receptor layer contains the photoreceptive outer segments (rods and cones) of receptor cells.
The pigmented epithelium absorbs light not captured by photoreceptors, and also contributes to the maintenance of rods and cone outer segments.
The red line between the outer nuclear layer and the receptor layer is the site of the outer limiting membrane, a basal lamina bounding the neural retina. The outer segments (rods and cones) of the receptor cells penetrate the outer membrane to contact the pigmented epithelium.
