Cranial nerve IX, also known as the glossopharyngeal nerve, is the ninth cranial nerve. It plays a crucial role in both sensory and motor functions. This nerve is responsible for taste sensations from the posterior one-third of the tongue and provides sensory input from the throat and tonsils. It also contributes to the regulation of blood pressure through its connection to the carotid body. In addition to its sensory functions, cranial nerve IX controls some muscles involved in swallowing. It innervates the stylopharyngeus muscle, which helps elevate the pharynx during swallowing. This nerve is essential for proper swallowing and contributes to the gag reflex.