Spinal cord central canal of the German shepherd dog: Morphological, histological, and ultrastructural considerations

Abstract

This study deals with some macroscopical, microscopical, and ultrastructural aspects of the spinal cord central canal of the German shepherd dog. The caudal end of the spinal cord is constituted by the conus medullaris, which may extend to the first sacral vertebra, the terminal ventricle, and the filum terminale. The latter structure is considered as internum (second to third sacral vertebrae) or externum (fifth caudal vertebra), according to its relation to the dura mater. Occasionally, there is a second anchorage which is close to the level of the sixth caudal vertebra. The central canal is surrounded by a ciliated ependymal epithelium, which differs depending upon the levels. The most caudal part of the filum terminale bears a columnar ciliated ependymal epithelium surrounded by two layers of glia and pia mater, which separate the central canal from the subarachnoid space. Microfil injections show a communication between the cavity and the subarachnoid space, as the plastic is able to pass through the ependymal epithelium. At the level of the terminal ventricle there are real separations of the ependymal epithelium, which seem to connect the lumen of the spinal canal with the subarachnoid space. These structures probably constitute one of the drainage pathways of the cerebrospinal fluid. The diameter of the central canal is related to the age of the animal. However, even in very old animals the spinal cord central canal reaches the tip of the filum terminale and remains patent until death. At the ultrastructural level the ependymal cells present villi, located on cytoplasmic projections, cilia, dense mitochondria, and oval nuclei.

The Segmental Morphometric Properties of the Horse Cervical Spinal Cord: A Study of Cadaver

“…Although the diameter of the central canal in the dog [45] is known to be associated with ageing, no information about occlusion of central canal caused by ageing, except in association with pathological conditions, has been found in the literature. It could be said that the central canal of healthy domestic animals is more functional and stable than that of humans, and thus it has a specific morphometry.…”

Identification and Characterization of Secondary Neural Tube-Derived Embryonic Neural Stem Cells In Vitro

“…These NSCs in the secondary neural stem cells (sNSCs) proliferate to form rosette-like structures, which subsequently undergo cavitation to form the lumen, which is continuous with the lumen of the tube formed during primary neurulation [3][4][5]. As development proceeds, the secondary neural tube becomes the filum terminale [6], which was shown recently to contain NSCs with a neuronal differentiation ability both in vivo and in vitro [7]. Defects in secondary neurulation can be diagnosed during the third trimester or at birth [8], raising the importance of understanding the properties of secondary neurulation and the cells that compose the early secondary neural tube, sNSCs.…”

The Human Central Canal of the Spinal Cord: A Comprehensive Review of its Anatomy, Embryology, Molecular Development, Variants, and Pathology

“…Studies of various species, including some primates and German shepherd dogs [17], have demonstrated openings from the filum terminale central canal into the subarachnoid space [7, 18-22]. …”