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→Slide 286, Ear Cochlea
== Eye ==
[[File:HistologicChapter19EyeDiagramUveitis.jpg|thumb|200px|Eye Diagram Uveitis]]=== Slide 285, : Eye (H&E) ===
The eyeball is composed of three principal layers.
=== Retina ===
[[File:HistologicChapter19Retina.Jpg|thumb|200px|Retina]]
The retina consists of two distinct layers, the neural retina (often called simply "the retina") and the pigmented epithelium.
*The receptor layer contains the photoreceptive outer segments (rods and cones) of receptor cells.
Photoreceptor cells come in two types, rods and cones. Rods are sensitive to dim light and provide night vision. Rods are more numerous in the peripheral retina. Cones need brighter light and provide daytime color vision. Cones are more prevalent in the vicinity of the fovea.
== Ear ==
[[File:HistologicChapter19EarDiagram.jpg|thumb|200px|Ear Diagram]]
The ear has three distinct regions -- outer ear, middle ear, and inner ear.
=== Cochlea ===
[[File:HistologicChapter19CochlearNerve.jpg|thumb|200px|Cochlear Nerve]]==== Slide 286, : Ear Cochlea (H&E) ====
The cochlea houses an elaborate configuration of membranous labyrinth and hair cells, called the organ of Corti, designed for auditory reception. The basic shape of the cochlea is that of a snail-shell, or tapering helix. The spiraling tunnel that forms the cochlea of the bony labyrinth is divided into three distinct channels by portions of the membranous labyrinth attached to bony ridges. The central column of the helical cochlea contains axons serving the organ of Corti on their way to the auditory nerve.
=== Endolymph and Perilymph ===
[[File:HistologicChapter19CristaAmpullaris.jpg|thumb|200px|Crista Ampullaris]]
The membranous labyrinth is filled with endolymph and is surrounded by perilymph. Endolymph is a unique fluid, with high K+ concentration and very low Na+ concentration. This endolymph provides the proper ionic environment for hair cell function. Endolymph is secreted by cells of the stria vascularis, along the scala media of the cochlea.
