Peripheral nerve. Coloured light micrograph (LM) of a section through a peripheral nerve. The nerve shown here consists of one fascicle (bundle) of nerve fibres. Each nerve fibre is surrounded by a myelin sheath and this in turn is surrounded by loose connective tissue (endoneurium) which contains fibroblasts and capillaries. The whole fascicle is surrounded by a layer of collangeous connective tissue (perineurium). The layers of connective tissue strengthen the fascicle.