The ansa cervicalis (or ansa hypoglossi in older literature) is a loop of nerves that are part of the cervical plexus. It lies superficial to the internal jugular vein in the carotid sheath.

Branches from the ansa cervicalis innervate three of the four infrahyoid muscles: thesternohyoid muscle, the sternothyroid muscle, and the omohyoid muscle.

26 下列有關頸襻（ansa cervicalis）之敘述，何者錯誤？

 其分枝支配肩胛舌骨肌（omohyoid muscle）之上段

 其上根（superior root）源自於第一頸椎神經之腹側枝（ventral ramus）

 貼附於頸動脈鞘（carotid sheath）前外方

 其分枝鎖骨上神經（supraclavicular nerves）負責部分頸部皮膚之感覺

ans D

it is a motor nerve!