Peripheral Nerve: Connective Tissue Components

Abstract

In a peripheral nerve, the individual nerve fibres are organised by connective tissue that consists of three distinct components, called endoneurium, perineurium, and epineurium. Each of the three components has specific functional tasks and morphological characteristics. All three components can be seen in the survey electron micrograph in panel A. An unmyelinated nerve fibre is visible in the centre. Three axons containing a dense cytoskeletal network of neurotubules and neurofilaments are enveloped by thin cytoplasm sheaths of a cell of Schwann (S). The nerve fibre is surrounded by the endoneurium, consisting mainly of a fine network of collagen fibrils (C). Collagen fibrils also hold together nerve fibres and blood capillaries in larger nerve fibre bundles and are closely related to the basal laminae of both the Schwann cell of the nerve fibre and the perineurial cells. Within the endoneurium, fibroblasts are sparse. It is assumed that most of the collagen of the endoneurium is produced by the cells of Schwann.