Caudal to the midbrain, the pons is approximately 2.5 cm in length and connects the midbrain to the medulla (eFig. 9.32B). The midline of the anterior surface has a shallow groove, the basilar groove, where the basilar artery resides along its course (eFig. 9.32B). On either side of the basilar groove, the pons has a prominent convex shape as a result of the vast number of fibers bridging through the pons to the cerebellum through the middle cerebellar peduncle. Along the anterolateral surface of the pons, cranial nerve V, the motor and sensory root of the trigeminal nerve, emerges (eFig. 9.33B). At the junction of the pons and medulla, from medial to lateral, cranial nerves VI (abducent), VII (facial), and VIII (vestibulocochlear) emerge (eFig. 9.33C). The posterior surface of the pons faces the cerebellum and forms the floor of the fourth ventricle (eFig. 9.32A). Along the midline of the posterior surface is a prominent bump, the facial colliculus, which represents the relationship between the facial nerve fibers as they wind around the nucleus of the abducent nerve (eFig. 9.33C).