Journal Article 顎二腹筋の外側を通る外頸動脈の一例
A case of external carotid artery lateral to the digastric muscle

田所, 治  ,  春日, 美理依  ,  前田, 信吾  ,  奥村, 雅代  ,  金銅, 英二  ,  矢ヶ﨑, 裕  ,  TADOKORO, OSAMU  ,  KASUGA, MIRII  ,  MAEDA, SHINGO  ,  OKUMURA, MASAYO  ,  KONDO, EIJI  ,  YAGASAKI, HIROSHI

41 ( 1 )  , pp.47 - 53 , 2015-06-30 , 松本歯科大学学会
An external carotid artery lateral to the posterior belly of the digastric, classified as type IV, was found on the right side of a ₇4–year–old male cadaver during a student dissection practice. The external carotid artery bifurcated from the common carotid artery at the level of the upper border of the hyoid bone. The artery gave rise to the superior thyroid artery, linguofacial trunk, and occipital artery, and ran lateral to the digastric. A long styloid process was found and the stylohyoid descended from it to the hyoid bone. The intermediate tendon of the digastric was deep in relation to the stylohyoid. The external carotid artery on the left side bifurcated from the common carotid artery at a level higher than on the right side. The thyroid–linguofacial trunk bifurcated from the level lower than bifurcation of the common carotid artery. The external carotid artery was lateral to the stylohyoid. An embryological consideration of the course of the type IV external carotid artery in the present case is described.
外頸動脈は,第三と第四頸椎のあいだ(甲状軟骨上縁)の高さで総頸動脈から分岐し,顎二腹筋後腹と茎突舌骨筋の深層(内側)で,茎突咽頭筋と茎突舌筋の浅層(外側)を通る.この経路をⅠ型(通常)として,顎二腹筋後腹と茎突舌骨筋のあいだを通るⅡ型,茎突舌骨筋の支配神経と顎二腹筋後腹のあいだを通るⅢ型,顎二腹筋後腹と茎突舌骨筋の浅層(外側)を通るⅣ型が分類されている(1) Fig. 1 参照).これら経路変異の 4 型のうち,Ⅳ型の出現頻度は0.2₅%1)と極めて低く,本邦では森田2),岡本ら3),異邦ではPisk4)の報告に留まる.今回我々は,平成24年度松本歯科大学解剖学実習において,顎二腹筋後腹の浅層(外側)を通る外頸動脈の一例に遭遇し,若干の知見を得たので,外頸動脈の経路変異に関する発生学的考察を加えて報告する.

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