| Lab 8 Peripheral Nervous System: 1) Index 2) Introduction 3) Things To identify 4) Nerve and Nerve Fibers 5) Nerve & Nerve Fibers II 6) Nerve & Nerve Fibers III 7) Dorsal Root Ganglion 8) Sympathetic Ganglion 9) Parasympathetic Ganglion 10)Practical |
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DORSAL ROOT GANGLION (SENSORY GANGLION OR SPINAL GANGLION) |
| # 60 - Dorsal root ganglion, human, H&E, 1.5 mm |
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In this slide of a section through a dorsal root ganglion, observe the large, pale staining ganglion cells. Note the granular basophilic cytoplasm, large round nucleus and prominent nucleolus. What would you estimate is the size of these cells? These neurons are surrounded by smaller cells with darkly staining nuclei. These smaller cells are the satellite cells which are the peripheral nervous system's counterparts of the neuroglia of the CNS. The satellite cells rest on a basal lamina of connective tissue which is continuous with the endoneurium. Nuclei of the fibroblasts of connective tissue are also visible. Nerve fibers (myelinated) can be seen coursing through the ganglion. You may see some yellow-brown pigmentation in the cytoplasm of some neurons. This is lipofuschin, undigestible material remaining in residual bodies (secondary vacuoles) after autophagocytosis of damaged cell organelles. This material increases with age in certain cells and is nicknamed"wear and tear" pigment. Note the pseudo-unipolar neurons and observe how satellite cells appear almost embedded in their cytoplasm. The prominent nucleoli of neurons is typical of this type of cell. Also note the Nissl substance in the cytoplasm of the ganglion cells. Be sure you understand the morphology of Nissl substance at the ultrastructural level. What makes up Nissl substaince? In pseudounipolar neurons, one axon divides close to the cell body into two processes, one of which becomes a "functional dendrite" (although it actually is a myelinated axon). The dorsal root ganglion is encapsulated in condensed C.T. that is continuous with the sheath of the peripheral nerves that enter and leave it. References: Gartner, p. 141, Fig. 3 - 4 (sensory ganglion or spinal ganglion) Ross, p. 287, Fig. 3 - 4 DiFiore, p. 93, Fig. 7-6 |
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This is a low power slide of the Dorsal Root Ganglion. The key to knowing that you are looking at Neurons in the DRG is by looking for the CENTRALLY LOCATED NUCLEI, indicated by the Red arrows. These Large nuerons are Psuedouniplor, Sensory (Afferent) Neurons. They are responsible for conveying information to the Central Nervous System. You can tell that these Neurons have huge cell bodies. These are some of the largest cells in the body. The larger the cell body, the further away the information is coming from. Red arrows - Central Nuclei of Sensory Neurons
This is a high power shot of the same section above. Notice the Central Nuclei, indicated by the Yellow arrows. Remember if you see these large Neurons with central nuclei, you are in the Dorsal Root Ganglion. The cell body of these neurons is packed with Nissle Substance, which are packs of ER to synthesize Neurotransmitter, that give it th purple-ish color. Remember, THERE IS NO NISSLE SUBSTANCE IN THE AXON. The white arrow are pointing to the nuclei of cells that surround each Sensory neuron called Satellite Cells. In the surrounding connective tissue it is also possible to find fibroblast synthesizing the collagen. Yellow arrow - Central Nuclei of DRG neurons White arrow - Satellite cells
Here is another High power shot of the DRG. The Yellow arrows are again displaying the Central Nuclei of these sensory neurons. The Red arrows are showing another example of Satellite Cells. THe blue arrow is pointing to what is known as Lipofusckin. These are left over undigested materials that collect in granules and look like what they are, waste that the cell can't get rid of. Yellow arrow - Central Nuclei Red arrow - Satellite Cells Blue arrow - Lipofusckin
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Dorsal Root Ganglion (Sensory Neurons)
Sensory Neuron (Pseudo-Unipolar)
Sensory Neuron (Lipofusckin) |
