Fiber components of the recurrent laryngeal nerve of the rat: a study by light and electron microscopy.

A quantitative study by light and electron microscopy of the recurrent laryngeal nerve (RLN) of the rat has been performed. The diameter of the myelinated fibers displayed a bimodal pattern, with a pronounced peak at 2-3 microns, and with a second peak at 4.5-7 microns. The number of small fibers was reduced at the termination of the nerve, indicating that many of the small fibers are distributed to the trachea and oesophagus as the nerve ascends in the neck. Upon comparison, no difference between right and left side was noted in numbers of myelinated fibers. The RLN was also found to contain numerous unmyelinated fibers. Most of these fibers were of the diameter size range 0.2-0.6 microns. The unmyelinated fibers constituted about 50-60% of all axons in the RLN.