Microcirculatory bed of the human trigeminal nerve.

Abstract

The structure and topography of the microcirculatory bed of the human trigeminal nerve are described. Details of microvascular morphology in the epi-, peri-, and endoneurium in different parts of the nerve are emphasized. The vascular bed of the trigeminal nerve was studied following injecting an aqueous solution of black ink and differentiating between microcirculatory components using silver nitrate impregnation. Morphometric parameters were statistically analyzed. Features of vascular organization that control blood flow are found within the pia mater of the trigeminal nerve root coverings, capsule and stroma of the trigeminal ganglion, and the epineurium and external layer of perineurium of extracranial branches. The precapillary arterioles, capillaries, postcapillary venules, and venules are situated in the internal layers of the perineurium. However, while the endoneurium contains only capillaries, the epineurium and external layers of the perineurium contain blood vessels whose features reflect a capability of adapting to a vascular change (transepineural arterioles, arteriolovenular anastomoses, and precapillary sphincters). The inner perineurium layer contains only precapillary sphincters. Results show that the make-up and topography of the microcirculatory bed throughout the trigeminal nerve are determined by features of the connective tissue components. Arteriolovenular anastomoses facilitate blood redistribution within the superficial layers of the trigeminal nerve, while precapillary sphincters and transepineural arterioles provide optimal regulation of blood flow in deeper layers of the nerve trunk.