P. Maringarcia et al., SPINAL-CORD CENTRAL CANAL OF THE GERMAN-SHEPHERD DOG - MORPHOLOGICAL,HISTOLOGICAL, AND ULTRASTRUCTURAL CONSIDERATIONS, Journal of morphology, 224(2), 1995, pp. 205-212
This study deals with some macroscopical, microscopical, and ultrastru
ctural aspects of the spinal cord central canal of the German shepherd
dog. The caudal end of the spinal cord is constituted by the conus me
dullaris, 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 cau
dal vertebra), according to its relation to the dura mater. Occasional
ly, there is a second anchorage which is close to the level of the six
th caudal vertebra. The central canal is surrounded by a ciliated epen
dymal epithelium, which differs depending upon the levels. The most ca
udal part of the filum terminale bears a columnar ciliated ependymal e
pithelium surrounded by two layers of glia and pia mater, which separa
te 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 epen
dymal 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 t
he 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 ultrastructura
l level the ependymal cells present villi, located on cytoplasmic proj
ections, cilia, dense mitochondria, and oval nuclei. (C) 1995 Wiley-Li
ss, Inc.