Diagram of the course and branches of a typical intercostal nerve. (Posterior division labeled at upper right.)
Areas of distribution of the cutaneous branches of the posterior divisions of the spinal nerves. The areas of the medial branches are in black, those of the lateral in red.
The posterior (or dorsal) branches (or divisions) of the spinal nerves are as a rule smaller than the anterior divisions.
They are directed backward, and, with the exceptions of those of the first cervical, the fourth and fifth sacral, and the coccygeal, divide into medial and lateral branches for the supply of the muscles and skin of the posterior part of the trunk.
