Both the left and the right S5 nerves and the coccygeal nerve of each side exit the sacral hiatus just medial to the sacral cornua of the same side. They proceed inferiorly and laterally, wrapping around the inferior tip of the sacral cornua (see Dorsal Surface). The posterior primary divisions (PPDs) of these nerves pass posteriorly and inferiorly to supply sensory innervation to the skin over the coccyx. The S5 and coccygeal anterior primary divisions (APDs) pass anteriorly to pierce the coccygeus muscle and enter the inferior aspect of the pelvis. Here they are joined by the ventral ramus of the S4 nerve to form the coccygeal plexus. This small plexus gives off the anococcygeal nerves that help to supply the skin adjacent to the sacrotuberous ligament.