The trigeminal nerve is the largest of the cranial nerves and branches into three divisions— the ophthalmic, maxillary, and mandibular division—controlling sensory functions. The maxillary and mandibular divisions travel through the upper and lower jawbones, respectively, reaching the epidermis through small openings in the bones, where they connect to the black spots known as integumentary sensory organs (ISOs). ISOs are densely distributed around the mouth, providing the crocodilian jaw a very high sensitivity.