These neurons leave the spinal cord in the ventral roots and project to skeletal muscle. It contains the cell bodies of lower motor neurons. The area of the grey matter closest to the front of the spinal cord is called the anterior horn. The substantia gelatinosa is an area of the posterior horn that is specialized to deal primarily with fibers carrying pain and temperature information. This area consists of cell bodies of interneurons whose processes don't leave the spinal cord and neurons whose processes enter ascending tracts to carry sensory information up the cord. The area closest to the back of the spinal cord is called the posterior horn. The grey matter consists of cell bodies of motor and sensory neurons, and is divided into three regions.
When you look at the spinal cord in cross-section (at any level) you will see what some describe as an H-shaped or a butterfly-shaped area of grey matter surrounded by white matter. In both cases, the filum terminale helps to anchor the cord in place. The filum terminale also extends from the end of the dural sheath to attach the spinal cord to the tailbone. The spinal cord is attached to the end of the dural sheath by a thin extension of the pia mater known as the filum terminale. This procedure is known as a lumbar puncture or spinal tap it is done from the lumbar cistern because there is little risk of damaging the spinal cord by inserting a needle there (since the cord is not present at that level of the vertebral canal). Cerebrospinal fluid is often taken from the lumbar cistern if it needs to be sampled for testing (e.g. These nerves travel through the lumbar cistern the straggly collection of fibers here is referred to as the cauda equina because it resembles a horse's tail. Additionally, although the conus medullaris is found at around L2, there are still several pairs of spinal nerves that must travel to the lower half of the body from the final segments of the cord. Because this extension of the meningeal covering of the cord-sometimes referred to as the dural sheath-continues past the end the cord, it creates a cerebrospinal fluid-filled cavity known as the lumbar cistern where there is no cord present. However, the spinal cord (like the brain) is surrounded by protective membranes known as the meninges, and the meningeal layers known as the dura mater and arachnoid mater continue for several more segments (to about the second sacral vertebrae) beyond the end of the cord itself. The spinal cord terminates in a cone-shaped structure called the conus medullaris, which is usually found at around the first or second lumbar vertebrae (L1-L2). Red = cervical, blue = thoracic, pink = lumbar, green = sacral. Spinal nerves by spinal cord segment they emerge from. Each area of the spinal cord from which a spinal nerve leaves is considered a segment and there are 31 segments in the spinal cord: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Spinal nerves travel to the periphery of the body there are 31 pairs of spinal nerves in total. The ventral root and dorsal root come together just beyond the dorsal root ganglion (moving away from the cord) to form a spinal nerve. The cell bodies for these sensory neurons are clustered together in a structure called the dorsal root ganglion, which is found alongside the spinal cord. Sensory information is carried by sensory neurons in dorsal roots, which enter the cord in small bundles called dorsal rootlets.
Motor neurons leave the cord in collections of nerves called ventral rootlets, which then coalesce to form a ventral root. The spinal cord also receives all of the sensory information from the periphery of our bodies, and contains pathways by which that sensory information is passed along to the brain. The spinal cord contains motor neurons that innervate skeletal muscle and allow for movement as well as motor tracts that carry directives for motor movement down from the brain. The spinal cord is one of the two major components of the central nervous system (the other being the brain) its proper functioning is absolutely essential to a healthy nervous system. What is the spinal cord and what does it do? It is only about 16.5-17.5 inches long on average, with a diameter of less than 1/2 an inch at its widest point. The spinal cord is shorter than the vertebral column, and overall is a surprisingly small structure. The spinal cord runs from the medulla oblongata of the brainstem down to the first or second lumbar vertebrae of the vertebral column (aka the spine). Close-up of spinal cord and dorsal and ventral roots.
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