A cross section of the spinal cord reveals the following features, shown in Figure 2: • Roots are branches of the spinal nerve that connect to the spinal cord. Two major roots form the following: • A ventral root (anterior or motor root) is the branch of the nerve that enters the ventral side of the spinal cord. Ventral roots contain motor nerve axons, transmitting nerve impulses from the spinal cord to skeletal muscles. • A dorsal root (posterior or sensory root) is the branch of a nerve that enters the dorsal side of the spinal cord. Dorsal roots contain sensory nerve fibers, transmitting nerve impulses from peripheral regions to the spinal cord. A dorsal root ganglion is a cluster of cell bodies of a sensory nerve. It is located on the dorsal root. • Gray matter appears in the center of the spinal cord in the form of the letter H (or a pair of butterfly wings) when viewed in cross section: • The gray commissure is the crossbar of the H. • The anterior (ventral) horns are gray matter areas at the front of each side of the H. Cell bodies of
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