<P> 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 . Additionally , the floor plate also secretes netrins . The netrins act as chemoattractants to decussation of pain and temperature sensory neurons in the alar plate across the anterior white commissure , where they then ascend towards the thalamus . Following the closure of the caudal neuropore and formation of the brain 's ventricles that contain the choroid plexus tissue , the central canal of the caudal spinal cord is filled with cerebrospinal fluid . </P>
<P> 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 . Additionally , the floor plate also secretes netrins . The netrins act as chemoattractants to decussation of pain and temperature sensory neurons in the alar plate across the anterior white commissure , where they then ascend towards the thalamus . Following the closure of the caudal neuropore and formation of the brain 's ventricles that contain the choroid plexus tissue , the central canal of the caudal spinal cord is filled with cerebrospinal fluid . </P>
hole in the tube surrounding the spinal cord
hole in the tube surrounding the spinal cord
the small central canal
the small central canal