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Shortly after exiting the intervertebral foramina, the spinal nerves branch into dorsal and ventral primary rami. Be careful! Dorsal primary rami and ventral primary rami are NOT the same as dorsal roots and ventral roots! Think of the spinal nerve as the trunk of a tree - the word ramus means branch in Latin, so the primary rami are the branches of a spinal nerve, whereas the roots unite to form the spinal nerve. These terms are very easy to confuse. The primary rami are mixed nerves carrying both motor and sensory fibers. The primary rami branch many, many times to provide innervation to almost the entire body. Nerves that branch from the dorsal primary rami supply the deep back muscles as well as the skin over the back. Nerves from the ventral primary rami supply the limbs and the rest of the trunk. |
