What is the Endoneurium?

The endoneurium, also called endoneurial cells, is the fibrous material that separates axons from one another within a peripheral nerve. Peripheral nerves contain multiple axons which can send information to different muscles. The endoneurium is needed to keep the signals separate so they arrive at the correct destination. These cells are also used to protect the delicate axons for becoming damaged.

Endoneurium is found within peripheral nerves. It is made up of connective tissue cells that surround a peripheral nerves’s axons. The axon is the cable-like structure that sends information from one side of a neuron to the other. The long neurons in a peripheral nerve are quite delicate and are surrounded by endoneurium cells for the entire length of the nerve. The endoneurium surrounds each axon independently, keeping them separate while providing structural support within the neuron.

Peripheral nerves require the fibrous endoneurium to function correctly. Made of collagen, these cells prevent information running along one axon from jumping to a different axon. Each neuron is completely surrounded by these cells, which successfully insulates neural signals.

The endoneurium cells have a secondary function as well. As they are made of collagen, a substance that is stronger than the axons in the nerve, they provide protection and support to the delicate communication system within the neuron. Along with the perineurium and the epineurium, the endoneurium helps to insulate the neurons from damage.

The peripheral nerves are one of the four components of the human nervous system. These nerves transport information to and from the body and the spinal cord. As they can be distant from the central nervous system, peripheral nerves can be as long as 3 feet (about 1 m). A normal nerve cell could become easily damaged at this length, so the peripheral nerves contain endoneurium to help buffer them from damage as well as to make sure signals traveling down the axons remain separate from one another.

All the systems within a peripheral nerve are remarkably adept at repairing themselves. The endoneurium can connect together again if severed and can continue to serve its function when the nerve is stretched or pulled. Indeed, even the axons themselves are capable of fusing back together if severed. This is unusual for nerve cells but, given the long length of peripheral nerves, advantageous. People who suffer injuries to these cells are usually able to make full recoveries with only minor loss of mobility or function.