the small central canal is the hole in the tube surrounding the spinal cord.
the small central canal is the hole in the tube surrounding the spinal cord.
hole in the tube surrounding the spinal cord?
the small central canal
the spinal cord is made from part of the neural tube during development. there are four stages of the spinal cord that arises from the neural tube: the neural plate, neural fold, neural tube, and the spinal cord. neural differentiation occurs within the spinal cord portion of the tube. as the neural tube begins to develop, the notochord begins to secrete a factor known as sonic hedgehog or shh. as a result, the floor plate then also begins to secrete shh, and this will induce the basal plate to develop motor neurons. during the maturation of the neural tube, its lateral walls thicken and form a longtitudinal groove called the sulcus limitans. this extends the length of the spinal cord into dorsal and ventral portions as well. meanwhile, the overlying ectoderm secretes bone morphogenetic protein (bmp). this induces the roof plate to begin to secrete bmp, which will induce the alar plate to develop sensory neurons. opposing gradients of such morphogens as bmp and shh form different domains of dividing cells along the dorsal ventral axis. dorsal root ganglion neurons differentiate from neural crest progenitors. as the dorsal and ventral column cells proliferate, the lumen of the neural tube narrows to form the small central canal of the spinal cord. the alar plate and the basal plate are separated by the sulcus limitans.
spinal cord
in tethered spinal cord cases spina bifida can be accompanied by tethering of the spinal cord but in rare cases with spina bifida occulta. tethering of the spinal cord tends to occur in the cases of spina bifida with mylomeningocele. in a normal person the spine grows faster than the spinal cord during development which causes the end of the spinal cord to appear to rise relative to the bony spine next to it. by the time of birth the spinal cord is located between l1 and l2. in a baby with spina bifida the spinal cord is still attached to the skin around it preventing it from rising properly. this occurs because the spinal cord in a child with spina bifida is low lying and tethered at the bottom. at the time of birth the mylomeningocele is separated from the skin but the spinal cord is still stuck in the same place. as the child begins to grow the spinal cord remains in the same place becoming stretched out causing the tight cord and the tethering at the end. with this type of tethering there is an interference with the blood supply to the nerves and body which can then cause the deterioration of the body causing orthopedic, neurological, and urological problems. with milder forms of spina bifida such as occulta, may be related to the degree of strain on the cord which can become worse with physical activity, injury, pregnancy, bone spurs, or spinal stenosis. the tethered cord in this case might not be diagnosed until adulthood when it worsens and can still cause neurological, orthopedic, and urological dysfunctions.
tethered spinal cord syndrome