Tongue Development Anterior 2/3 of tongue derived from 1st branchial arch sensation: lingual branch of CN V3 taste: chorda tympani branch of CN VII Posterior 1/3 derived from 3rd and 4th branchial arches sensation and taste: CN IX extreme posterior sensation and taste: CN X Motor innervation all muscles of tongue: CN XII except palatoglossus (CN X) muscles of tongue are derived from myoblasts originating from the occipital somites Thyroid Development Thyroid diverticulum develops from endodermal lining of foregut appears from the midline of the floor of the primitive pharynx descends into the neck maintaining a connection to the tongue through the thyroglossal duct thyroglossal duct degenerates during development may remain as pyramidal lobe of thyroid foramen cecum: remnant of thyroglossal duct Thyroglossal duct cyst persistent thyroglossal duct forming a cyst in midline of neck near hyoid bone other location is at base of tongue: lingual cyst cyst moves during swallowing Ectopic thyroid tissue failure of migration downward can result in ectopic thyroid tissue forming anywhere along the thyroglossal duct's path tongue is the most common site of ectopic thyroid tissue