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

 

Nerve & Nerve Fibers II

 

2. #64 - Peripheral nerve, primate, l.s. and c.s., Mallory stain

 

Slide 64 is useful for studying the connective tissue (epineurium, perineurium and endoneurium) which is associated with the nerve fibers, This Mallory stain preparation stains collagen and reticular fibers blue, and nuclei, muscles and nerve axons red. Compare its appearance to the H&E stained Slide 62 you just examined.

Locate the epineurium surrounding the entire nerve trunk. Can you find continuities between it and the perineurium which surrrounds each fascicle or bundle of nerve fibers?

Locate the axons which appear as darkly staining strands surrounded by what appears to be vacuolated material. This material is the Schwann cell with the myelin dissolved away during preparation of the tissue. If this were a silver stained preparation, external to the neurilemma (of Schwann cell and myelin) you might observe the intensely agyrophilic reticular fibers of the endoneurium which surrounds each Schwann cell [Gartner, p. 125, Fig. 3 (inset)].

What is a non-myelinated nerve fiber? Do these fibers have a Schwann cell sheath? What is a neurilemma?

References: Gartner, p. 142-143, Fig. 1 - 3 p. 144-145, Fig. 1 (EM) Wheater, p. 126 - 127, Fig. 7.13, 7.14, 7.15 p. 128, Fig. 7.16 DiFiore, p. 93 - 95, Fig. 7-7 - 7-13

 

This is a cross section of a peripheral nerve. Here are three levels of connective tissue that surrounds the nerve fibers can be found. First, Epineurium which surrounds the entir peripheral nerve is indicated by the blue arrows. The next level is the Perineurium, which subdivides the nerve into fasicles indicated by the green arrows. The Perineurium has a special layer of epithelial cells that act as an extra layer of protection to keep infections out. How many fasicles in view here? Two.

The final level of covering is the Endoneurium which is indicated by the red arrows. This is the connective tissue that surrounds the individual nerve fibers.

Blue arrow - Epineurium

Green arrow - Perineurium

Red arrow - Endoneurium

Nerve (cross section)

 

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