Human Ependyma as a Sensory Organ

Abstract

No nerve cells have been proved in the human ependyma.
The sensory fibres supplying the ependyma probably come from the meningeal nerves originating in sensory cerebral nerves. They penetrate into the SILVI's duct through its caudal dorsal side and into the fourth ventricle from its lateral side near the central canal in the medulla oblongata, in small bundles, finally to form free terminations close under or within the ependyma. The subependymal terminations represent the main and the intraependymal fibres the subordinate terminations.
The subependymal terminations are divided into the simple typed and the complex typed. They are fluctuating in their local frequency, being very scarce in the central canal of the medulla oblongata, while simple typed ones are more frequent in the fossa rhomboidea, especially on its outer sides, and both simple and complex types are found in the SYLVI's duct, especially in its dorsal wall. Besides, some special sensory receptors are found in the dorsal central gray matter of the SYLVI's duct.
The simple typed terminations consist of one or two each of thick fibres, which show the peculiarities of common peripheral sensory fibres in their terminal areas, and form uncircumscribed branched terminations. Some of the branches show specially shaped fibril distensions in their courses or at their tips. Some of them run into the ependyma to go over into intraependymal fibres. These simple terminations contain special glial cell nuclei, smaller in number than in the complex typed ones. These cells probably effect special internal secretion concerned with the transmission of stimuli.
The complex typed terminations are composed of two or three each of thick fibres, which run far more complicated winding courses and send out more numerous branches than in the simple typed ones, and end in uncircumscribed complex branched terminations. The branches generally end in sharp points, but before terminating or at their ends often form two kinds of peculiar terminal bodies, the one of which consists of fibril distensions of larger sizes and variable forms and the other of small nodular distensions formed at the tips of many short rami which are divided again from the terminal branches. These formations are called racemose terminations.
The receptive area at the dorsal side of the SILVI's duct is nearly triangular in shape, and the special terminations therein are each composed of a ground tissue with numerous special cell nuclei and thick and thin fibres running into it. The thick fibres oftener run peculiar ansiform courses.
The intraependymal fibres are small in number but evenly distributed over all the central cavity. Some of them are thick fibres which directly run into the ependyma through the subependymal tissue, and the others originating in the subependymal terminations. They are usually represented as unbranched or simple branched terminations and run both between and through the ependymal cell bodies.
The receptive organ in the brain comprises beside the pia mater (STÖHR) also the ependyma. The physiological function of the sensory terminations connected with the ependyma consists in the reception of the stimuli caused by the physical and chemical changes of the cerebrospinal liquor, and concerns the mechanism of its flow regulation and the adjustment of its chemical composition. We assume that these sensory terminations cause the phenomea of headache, vertigo, nausea, vomitting etc. in pathological cases.