(from Greek, derma: skin, tomos, section) The SKIN surface can be divided into dermatomes. The dermatomes partially overlap, but each one projects to a particular DORSAL ROOT of the SPINAL CORD, meaning that different parts of the spinal cord are collecting information from different parts of the body. In the upper body the relationship between the spinal cord and dermatomes is fairly straightforward: the CERVICAL SPINAL CORD (at the top) collects information from dermatomes on the back of the head (the face having its own CRANIAL NERVES), neck, shoulders, arms and hands; the THORACIC SPINAL CORD below it collects information from dermatomes around the trunk.
But the relationship between the lower body dermatomes and spinal cord is a little more complicated. The hips, front of the legs and upper parts of the feet send information into the dorsal roots of the LUMBAR SPINAL CORD, while the back of the buttocks, backs of the legs, sides and sides of the feet send information to the dorsal roots of the sacral spinal cord. This arrangement appears slightly odd on a BIPED, but reflects quite well the stance of a QUADRUPED: if one bends forwards with one’s hand almost touching the floor, the dermatome-spinal cord relationship becomes clearer, sacral spinal cord innervating the most poster ior parts of the body, the cervical the most anterior. The size of dermatomes can be examined by touch with a pin prick. In cases of spinal cord damage, the absence of sensation in dermatomes can reveal much about the location of spinal injury.
