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The Retina

Objective 2: Discuss the microscopic anatomy of the retina.

 

Photomicrograph of a flattened mouse retina.

 

 

 

The retina extends from the edges of the ciliary body, lining the interior of the eye.

 

 

 

 

Photograph of the fundus of a human eye.

 

 

In the direct path of the photons which pass through the pupil without being refracted (i.e. without the light rays being bent) is a pit called the fovea centralis (“central pit”). This region has a high concentration of yellowish visual pigment and so is also called the macula lutea (“yellow spot”).

 

 

Photomicrograph of the human eye.
A photomicrograph of the human eye. For reasons lost to the sands of time, PhDs who study the eye always orient the photoreceptor outer segments sticking up.
Cross-section of the eye with a detailed diagram of the layers of the retina.
On the other hand, MD ophthalmologists, and those who make diagrams for them, orient the photoreceptor outer segments pointing downward. (The box which marks the enlarged region is not properly placed in this diagram and should be near the fovea. The photoreceptors point to the outside of the eye; light arrives from the inside of the eye.)

There are two types of photoreceptors, named after the distinctive shape of their modified cilia. In each case, the photoreceptor outer segments consist of stacks of membranes like a roll of pennies. The outer segment is connected to the cell body via a thin stalk.

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Introduction to Neuroscience Copyright © by Jim Hutchins; Lindsey Aune; and Rachel Jessop is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License, except where otherwise noted.

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