WORKSHOP ON HISTOLOGY, CYTOLOGY AND EMBRYOLOGY - 2016

Chapter 5. SPECIAL HISTOLOGY

Nervous system and sense organs.

Slide 73. Retina (posterior wall of the eye).

Staining: hematoxylin and eosin.

Magnification: x400.

Under low magnification, the slide should be positioned so that the sclera (1), identifiable by its light pink coloration, is at the top. Beneath it lie the choroid (2) and the retina.

The choroid is recognized by the abundant pigment and Blood Vessels located within it. Following the choroid is the retinal pigment epithelium (3). Thin processes filled with black pigment extend from the bodies of pigment Cells (melanocytes) deep into the underlying layer of rods and cones (4). The rod and cone layer is formed by the light-sensitive outer segments of the first (photoreceptor) neuron and appears on the slide as a light-pink, translucent strip with fine striation. The Cell bodies and nuclei of these Neurons form the outer nuclear layer (5), while their axons make up the deeper outer plexiform layer (6), which is light pink with isolated nuclei. From the rods and cones, excitation is transmitted to bipolar neurons, whose cell bodies form the inner nuclear layer (7), and whose axons form the inner plexiform layer (8). Here, synaptic contact and transmission of excitation from bipolar to multipolar ganglion neurocytes take place. The bodies of ganglion neurons are arranged at certain intervals to form the ganglion cell layer of the retina (9). The innermost layer is the nerve fiber layer (10)—consisting of neuron axons that converge to form the optic disc. The retina is separated from the vitreous body by the internal limiting membrane (11), which is composed of glial cell processes. The bodies of these radial glial cells are located in the center of the inner nuclear layer, and their peripheral ends tightly abut each other to form the external limiting membrane (12) at the boundary between the rod and cone layer and the outer nuclear layer. The diagram on the left illustrates the neural circuitry of the retina.

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Slide 73. Retina (posterior wall of the eye).