Peripheral nerve: Investments

At higher magnification the histological distinctions between the perineurium and epineurium are seen.  The perineurium is more basophilic, highly cellular and very compact.  In contrast, the epineurium is more eosinophilic, contains collagen fibers and fewer cells.  Note myelinated axons of various sizes and Schwann cell nuclei.  400x

The cells of the perinerium are highly unique and contribute to the formation of the protective blood-nerve barrier.  The cells are squamous and exhibit epithelial features, such as individual basal laminae and tight junctions.  However, they are also contractile, possess large numbers of actin filaments, and synthesize collagen and, thus, resemble smooth muscle cells and fibroblasts.

The epineurium consists of a dense irregular connective tissue of collagen bundles that blends with the surrounding connective tissue.  Epineurium surrounds larger trunks of peripheral nerves and is lost as peripheral nerves decrease in size.

At higher magnification the histological distinctions between the perineurium and epineurium are seen.  The perineurium is more basophilic, highly cellular and very compact.  In contrast, the epineurium is more eosinophilic, contains collagen fibers and fewer cells.  Note myelinated axons of various sizes and Schwann cell nuclei.  400x

At higher magnification the histological distinctions between the perineurium and epineurium are seen.  The perineurium is more basophilic, highly cellular and very compact.  In contrast, the epineurium is more eosinophilic, contains collagen fibers and fewer cells.  Note myelinated axons of various sizes and Schwann cell nuclei.  400x

At higher magnification the histological distinctions between the perineurium and epineurium are seen.  The perineurium is more basophilic, highly cellular and very compact.  In contrast, the epineurium is more eosinophilic, contains collagen fibers and fewer cells.  Note myelinated axons of various sizes and Schwann cell nuclei.  400x