NERVES – 5
The upper figure shows part of a cross-sectioned myelinated nerve.
The majority of its nerve fibers are arranged along the nerve longitudinal axis and are seen cross-sectioned.
The dark circles seen inside each fiber are axons.
Most axons of the perypheral nervous system are covered by folds of Schwann cell cytoplasm. The cell membranes of the folds shown in this figure were converted into myelin, hence, this is a myelinated nerve.
Myelin is basically constituted by fat. It was dissolved and lost during the preparation of this section. For this reason the spaces that originally contained the myelin sheath appear to be empty.
The loose connective tissue of the endoneurium placed between nerve fibers is usually scarce. The pink stained areas between axons in the lower figure represent the endoneurium.
The unstained empty spaces between nerve facicles and between groups of fibers are technical artifacts that resulted from tissue retraction introduced during the histological technique.
The lower figure is a higher magnfication of an area of the upper figure. It shows axons highlighted in blue, Schwann cells cytoplasm in green. The nucleus of one of the Swchwann cells is highlighted in dark green.
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Nerve (cross section). Staining: HE. Medium magnification.
This lower figure shows details of: Schwann cell cytoplasm (highlighted in light green), a Schwann cell nucleus (in dark green) and axons (in blue).
Nerve (cross section). Staining: HE. Medium magnification.
