| Epineurium | |
|---|---|
 Transverse section of humantibial nerve. (Epineurium labeled at upper right.) | |
 Nerve structure | |
| Details | |
| Identifiers | |
| Latin | Epineurium |
| TA98 | A14.2.00.016 |
| TA2 | 6155 |
| FMA | 12234 |
| Anatomical terminology | |
Theepineurium is the outermost layer of dense irregularconnective tissue surrounding a peripheralnerve.[1][2] It usually surrounds multiplenerve fascicles as well asblood vessels which supply the nerve. Smaller branches of these blood vessels penetrate into theperineurium.[3] In addition to blood vessels which supply the nerve, lymphocytes and fibroblasts are also present and contribute to the production of collagen fibers that form the backbone of the epineurium. In addition to providing structural support,lymphocytes andfibroblasts also play a vital role in maintenance and repair of the surrounding tissues.[4]
When thespinal nerve leaves thevertebral canal via anintervertebral foramen, two layers of thespinal meninges, thearachnoid and thedura invaginate the nerve to form a dural sleeve of connective tissue, which is the epineurium. The outer portion of this sleeve comprises the external epineurium which permits longitudinal nerve excursion and absorption of longitudinal stress. The layer of the epineurium that extends within the nerve to define the fascicles is termed the internal epineurium. Together, these two layers form the epineurium, which varies in thickness along the course of a nerve.[5] The epineurium is usually most abundant around joints, as its function is to protect the nerves from stretching and subsequent injury. Epineurium is primarily made fromcollagen.[3]
A commonsurgical procedure to repair atorn nerve via the epineurium is termed anepineurial repair.[6]
Schwannomas often remain completely encapsulated by the epineurium as they grow.[7]
Epineurial barriers can be used to limit the formation ofneuromas afterneurotmesis.[8] The epineurium is an effective barrier againstaxon growth.[8]
