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Peripheral nerve: Investments
This cross section of a peripheral nerve is stained with the Masson stain to reveal its investing layers. Individual axons and their sheaths are surrounded by an endoneurium. Groups of axons form a fascicle enclosed by a perineurium. This peripheral nerve, composed of a single fascicle, retains only a thin, fragmented rim of epineurium around its periphery. 400x

Axons
This cross section of a peripheral nerve is stained with the Masson stain to reveal its investing layers. Individual axons and their sheaths are surrounded by an endoneurium. Groups of axons form a fascicle enclosed by a perineurium. This peripheral nerve, composed of a single fascicle, retains only a thin, fragmented rim of epineurium around its periphery. 400x

Myelin sheaths
This cross section of a peripheral nerve is stained with the Masson stain to reveal its investing layers. Individual axons and their sheaths are surrounded by an endoneurium. Groups of axons form a fascicle enclosed by a perineurium. This peripheral nerve, composed of a single fascicle, retains only a thin, fragmented rim of epineurium around its periphery. 400x

Endoneurium >
The endoneurium, stained green with this procedure, surrounds individual axons and consists of loose connective tissue.

Perineurium
This cross section of a peripheral nerve is stained with the Masson stain to reveal its investing layers. Individual axons and their sheaths are surrounded by an endoneurium. Groups of axons form a fascicle enclosed by a perineurium. This peripheral nerve, composed of a single fascicle, retains only a thin, fragmented rim of epineurium around its periphery. 400x

Epineurium
This cross section of a peripheral nerve is stained with the Masson stain to reveal its investing layers. Individual axons and their sheaths are surrounded by an endoneurium. Groups of axons form a fascicle enclosed by a perineurium. This peripheral nerve, composed of a single fascicle, retains only a thin, fragmented rim of epineurium around its periphery. 400x