Unsourced material may be challenged and removed. The enclosing bony vertebral column protects the relatively shorter spinal cord. The cervical enlargement, stretching from the C5 to T1 vertebrae, is where cross sectional anatomy brain pdf input comes from and motor output goes to the arms and trunk.
The lumbar enlargement, located between L1 and S3, handles sensory input and motor output coming from and going to the legs. It does not run the full length of the vertebral column in adults. It is made of 31 segments from which branch one pair of sensory nerve roots and one pair of motor nerve roots. The delicate pia mater, the innermost protective layer, is tightly associated with the surface of the spinal cord. The spinal cord is elliptical in cross section, being compressed dorsolaterally. Two prominent grooves, or sulci, run along its length. Gray 111 – Vertebral column-coloured.
Six to eight motor nerve rootlets branch out of right and left ventro lateral sulci in a very orderly manner. Nerve rootlets combine to form nerve roots. Likewise, sensory nerve rootlets form off right and left dorsal lateral sulci and form sensory nerve roots. These rootlets form the demarcation between the central and peripheral nervous systems. Model of a section of a spine.
Columns” of white matter carry information either up or down the spinal cord. The cauda equina forms because the spinal cord stops growing in length at about age four, even though the vertebral column continues to lengthen until adulthood. This results in sacral spinal nerves originating in the upper lumbar region. Within the CNS, nerve cell bodies are generally organized into functional clusters, called nuclei. Axons within the CNS are grouped into tracts. In the fetus, vertebral segments correspond with spinal cord segments. L2 vertebral level, forming a structure known as the conus medullaris.
L2 vertebral level, the spinal nerves for each segment exit at the level of the corresponding vertebra. As these nerves travel from their respective roots to their point of exit from the vertebral column, the nerves of the lower spinal segments form a bundle called the cauda equina. It includes spinal cord segments from about C4 to T1. It comprises the spinal cord segments from L2 to S3 and is found about the vertebral levels of T9 to T12.
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. This extends the length of the spinal cord into dorsal and ventral portions as well. 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. 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. Overall, spontaneous embryonic activity has been shown to play a role in neuron and muscle development but is probably not involved in the initial formation of connections between spinal neurons. The spinal cord is supplied with blood by three arteries that run along its length starting in the brain, and many arteries that approach it through the sides of the spinal column. The actual blood flow caudally through these arteries, derived from the posterior cerebral circulation, is inadequate to maintain the spinal cord beyond the cervical segments. These intercostal and lumbar radicular arteries arise from the aorta, provide major anastomoses and supplement the blood flow to the spinal cord. L1 and L2, but can arise anywhere from T9 to L5.