Perineurium

Connective tissue sheath surrounding nerve fascicles

The perineurium is a protective sheath that surrounds bundles of nerve fibers, known as nerve fascicles. It is a critical component of the peripheral nervous system, providing both mechanical protection and a biochemical barrier to the enclosed nerve fibers.

Diagram of a nerve, showing the perineurium surrounding each fascicle.

Structure

The perineurium is composed of several concentric layers of flattened cells, which are connected by tight junctions. These cells form a continuous barrier that is impermeable to most macromolecules, thus maintaining the blood-nerve barrier. The perineurium is situated between the epineurium, which encases the entire nerve, and the endoneurium, which surrounds individual nerve fibers within the fascicle.

Function

The primary function of the perineurium is to protect nerve fibers from mechanical injury and to maintain the internal environment of the nerve fascicles. It regulates the passage of substances between the bloodstream and the nerve fibers, thus playing a crucial role in maintaining the homeostasis of the nerve tissue.

Clinical significance

Damage to the perineurium can lead to neuropathy, as the protective barrier is compromised, allowing potentially harmful substances to affect the nerve fibers. Surgical repair of nerve injuries often involves careful reconstruction of the perineurium to restore its protective functions.

Related pages

• Nerve
• Epineurium
• Endoneurium
• Peripheral nervous system