Review Question - QID 212899

Item D in Figure B represents the perineurium, the fibrous tissue covering fascicles.

The basic building blocks of nerves are the axons of the individual nerve cells (neurons). The axons are covered by a myelin sheath that is produced by Schwann cells and speeds nerve conduction. These myelinated axons are bundled together to form a fascicle. The connective tissue and capillary network that supports the nerve fibers within each fascicle is called the endoneurium. Fascicles are grouped together into another connective tissue network, the perineurium, which provides mechanical strength to the nerve. Multiple groups of nerve fascicles are surrounded and sheathed by the epineurium, which provides support and vascularity.

Lee et al. published a review on peripheral nerve injury and repair. They review the cross-sectional anatomy of a peripheral nerve, which includes the epineurium, perineurium, fascicle, endoneurium, and axon. They also review the classification, treatment, and outcomes of nerve injuries. They report that outcomes of nerve repair to date have been no better than fair, with only 50% of patients regaining useful function.

Figure A is a clinical image of a deep laceration to the volar aspect of the proximal forearm. Figure B is an image demonstrating the cross-sectonal anatomy of a peripheral nerve, including the nerve fiber (A), myelin (B), epineurium (C), perineurium (D), endoneurium (E), and node of Ranvier (F).

Incorrect Answers:
Answer 1: The epineurium is indicated by Item C.
Answer 3: The nerve fiber is indicated by Item A.
Answer 4: Myelin is indicated by Item B.
Answer 5: The endoneurium is indicated by Item E.