Date of Award

8-1-1966

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomedical Sciences

Abstract

Electron microscopy has settled prior controversies regarding the relationship of axon, myelin and Schwann cell bat doubt remains about the correct interpretation of the classic binding sheaths. Perineurium is customarily interpreted to be flattened fibroblasts but recent evidence suggests attenuated Schwann cells. This study attempts to reinterpret the morphology of peripheral nerve known to be fixed adequately for fine structure. Special emphasis is placed on the binding sheaths, especially perineurium.

Forty white rats were perfused with buffered aldehydes. Sural and sciatic nerves were removed. Smaller nerves were obtained with orbital contents and the loose connective tissue of spleen and pancreas. These were prepared for light microscopy with the least possible change of routine techniques. Selective chromatic stains were modified to demonstrate nerve morphology.

In this study perineurium is distinguished from epineurium and endoneurium because its boundary membranes stain with the periodic acid. Schiff (PAS) method and counterstains. Additional stains also show perineurium as a distinct morphological layer that is complete and organized. Blood vessels are surrounded by perineurium in their longitudinal course within this sheath. All nerve branches acquire a perineural covering from a parent nerve by a process of gradual partitioning.

Perineurium is demonstrable as a specialized layer. It resembles Schwann cells by reason of its boundary membranes and "wrap-around" tendencies. This suggests neuroectodermal rather than mesodermal origin. Tissue space with its contained connective tissues exists both inside and outside of perineurium.

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