21 迷走神經(vagus nerve)行經: (A)頸動脈管(carotid canal)離開顱腔 (B)鎖骨下動脈(subclavian artery)之前方 (C)脊柱(vertebral column)兩側支配消化腺 (D)頸動脈鞘(carotid sheath),與交感神經幹(sympathetic trunk)併行