The openings of the central canal in the filum terminale internum of some mammals

Abstract

Openings of the central canal in the filum terminale internum of the rabbit, guinea pig, and rat have been studied by light and electron microscopy. There were two openings in the rabbit, two or three in the guinea pig, and one in the rat. They opened dorsally and were of two types; one type was without a pial covering, the other with a pial covering. In both types, a focal junctional apparatus associated with increased density of the subjacent cytoplasm was observed between the pial cell and the ependymal cell at the margins of the opening, where the basal lamina on the surface of the filum terminale showed a characteristic ending for each species. Injections of india ink into the lateral ventricle of the brain indicated that the cerebrospinal fluid of the ventricular system drains out of the central canal by way of these openings, into the subarachnoid space. Reissner's fibre of the rabbit and rat consisted of a mass of moderately electron dense fibrous material containing many small vesicles in the central canal of the filum terminale. This mass passed through the openings into the subarachnoid space and continued into the subdual space.

Characterization of the Filum terminale as a neural progenitor cell niche in both rats and humans

“…They also identified neurons using electrophysiology followed by dye‐filling (Chvatal et al, ). A similar organization of cellular elements around the central canal has also been observed in the FT of rabbits, guinea pigs, and rats by Nakayama ().…”

“…The filum terminale (FT) is a thin band of tissue that connects the spinal cord to the periosteum of the coccyx. It is present in all vertebrates and has been studied in a variety of species, including frogs, cats, rodents, and humans (Gamble, ; Nakayama, ; Gonzalez‐Robles and Glusman, ; Chesler and Nicholson, ; Rethelyi et al, ; Boros et al, ). Although it is continuous with the spinal cord, the FT has a unique developmental history, which involves regression from a differentiated state to that of a more primitive tissue.…”

The regulation of brain states by neuroactive substances distributed via the cerebrospinal fluid; a review

“…In the central canal of the rat spinal cord, CSF has been observed to continue flowing caudally at a speed of about 1 cm/min [60]. At the caudal tip of the spinal cord in the filum terminale, one opening (rat) or several openings (guinea pig, rabbit) (Fig 1) allow the CSF to access the subarachnoid space [61]. The CSF surrounding the spinal cord may either rapidly re-enter the spinal cord and central canal via perivascular spaces [62], or leave perispinal spaces to be released into lymphatic or venous vessels [63].…”

The perineurial vessel: A possible candidate for the structural basis of the meridian (Jing-Luo) in Chinese medicine*

“…Conversely, the fact that the CSF equals the tissue fluid of the nervous system is not so well recognized, especially for peripheral nerves. The CSF, which is secreted from the choroid plexus epithelium into the ventricles, flows down the ventricular system to the fourth ventricle to escape into the subarachnoid space through the foramina of Magendie and Luschka, and also down the central canal to the terminal ventricle to escape into the spinal subarachnoid space through the foramen of Nakayama (Nakayama, 1976;Sakata et al, 1993). It then flows up to the brain stem to be absorbed into the fenestrated venous capillaries of the choroid plexus and of neighboring circumventricular organs as the tissue fluid of the central nervous system, because the propria of these organs equals the subarachnoid connective tissue (Figs 1,2).…”

“…At the root of every peripheral nerve, the CSF continues within the perineurial vessel as the tissue fluid of the peripheral nerve, with a positive fluid pressure and a very slow proximodistal flow, as mentioned already. Nakayama (1976) and Sakata et al (1993).…”