EVERYDAY SCIENCE

Detailed explanation-1: -Taste to the anterior two-thirds of the tongue is achieved through innervation from the chorda tympani nerve, a branch of the facial nerve (CN VII).

Detailed explanation-2: -Consequently, lesions of the root of the seventh cranial nerve or tumors in the internal auditory meatus, such as a vestibular schwannoma, sometimes called an acoustic neuroma (see Fig. 22-10), will result in loss of taste perception from the anterior two thirds of the tongue on the ipsilateral side.

Detailed explanation-3: -The 7th cranial nerve also has some sensory component including the sense of taste (anterior 2/3 of the tongue).

Detailed explanation-4: -The tongue itself is divided into 2 sections. There is the oral part which is the anterior 2/3 which lies in the oral cavity proper and a pharyngeal part which is the posterior 1/3 of the tongue which lies in the oropharynx area.

Detailed explanation-5: -Test the anterior 2/3’s of the tongue (CN VII) by alternately placing two to three familiar liquids on each side of the anterior 2/3’s of the tongue (pictured to the right). Also, test the posterior 1/3 of the tongue (CN IX) in a similar manner. Document normal or abnormal responses.