Histology 17: Nsu Spring 2009 Taken By: Gregory Rodocker

Histology 17 NSU Spring 2009 Taken by: Gregory Rodocker

Photoreceptor and Audioreceptor Systems 

The Eye 

Complex, highly developed photosensitive organ   

Form Light intensity Color

External Layer: Tunica fibrosa 

Sclera 



Tough, white opaque layer of dense CT with few fibroblasts on five sixths of the eyeball exterior

Cornea 

Colorless, transparent multilayered structure that allows light to enter

Middle or Vascular Layer 

Actually contains the following structures:   

Choroid Ciliary body Iris

Choroid 



Highly vascularized loose CT filled layer containing fibroblasts, macrophages, lymphocytes, mast cells, plasma cells, collagen fibers and elastic fibers Melanocytes also present giving the layer its characteristic black coloration

Ciliary body  

Anterior extension of the choroid Contains several sets of muscles that function in visual accommodation

Ciliary processes

Ciliary processes   

Loose CT core Fenestrated capillaries Produces the aqueous humor 





Similar to plasma but with 0.1 % protein compared to 7% in plasma Travel through pupil to anterior chamber and drains via canal of Schlemm

Anchors lens in place via zonular fibers

Iris  





Extension of choroid Contains the round opening called the pupil Loose CT, Fibroblasts and melanocytes Dilator and sphincter pupillae muscles

Photo opposite from one in book

Lens   

Lens capsule Subcapsular Epithelium Lens fibers

Accommodation 



Lens is stretched when looking at distant objects by elasticity of ciliary body To focus closer in, the ciliary muscles contract; zonular fiber tension is relieved and the lens thickens

Retina   



Innermost layer of the eye Posterior photosensitive portion and Anterior part covering ciliary body and iris Layers of photosensitive portion  

Pigmented epithelium Neural portion

The Ear  

Internal Ear Membranous labyrinth    

Cochlea Utricle Saccule Semicircular canals

Receptor hair cells 

Each has 40-80 rigid stereocilia (microvilli) and one cilium (kinocilium)