A branch of the facial nerve (CN VII) that runs through the middle ear and exits the base of the skull at the petrotympanic fissure, where it joins the lingual nerve. The chorda tympani carries preganglionic parasympathetic secretomotor fibers to the submandibular and sublingual glands, afferent taste fibers from the anterior 2/3 of the tongue, and sensation from the posterior wall of the external acoustic meatus.