Microanatomical structure of the human sciatic nerve

Sciatic nerve is the largest peripheral nerve of the human body. It gives motor and sensitive innervation for the most of lower limb. The aim of the present investigation was revealing his fascicular pattern in relation to microanatomic morphometric characteristics of its connective tissue sheaths.

The material consisted of sciatic nerve slices, excised from 17 cadavers of humans aging 8-93 years. After routine histologic processing and light microscopic examination of the preparations, morphometric analysis was performed at magnifications of 40 and 630x.

Sciatic nerve showed to be polyfascicular nerve type, with the group pattern of nerve fascicless distribution. The number of fascicless ranged from 27 to 70, whereas the number of fascicless per square millimeter was 1-4. Morphometric and correlation analysis confirmed the significant increase of whole sciatic nerve cross section area, which was associated with the significant increase of its epi- and perineural connective tissue sheaths. Interfascicular sciatic nerve domains of elderly persons contained more adipose tissue. Moreover, already detected loss and degeneration of the large myelinated nerve fibers within fascicles was accompanied by the significant increase of endoneural connective tissue.

In conclusion, our study revealed comparative connective tissue enlargement of human sciatic nerve in the course of aging. These phenomena might influence on result of injured nerve's surgical reparations. We interpret this finding as non-specific compensatory phenomenon elicited by loss of thickest myelinated nerve fibers, higher vulnerability of remaining ones, and age-dependent decrease of connective tissue elasticity.