Exposure of left subclavian artery by supraclavicular approach does not require cutting of:
Ans. is 'c' i.e. Scalenus medius Scalenus medius lies posterior to the subclavian artery and thus need not be divided to expose the artery. Whereas, sternocleidomastoid & scalenus anterior lie anteriorly and omohyoid lies superiorly and thus are cut during exposure of the subclavian artery.Relation of the subclavian arteryThe right subclavian artery arises from the brachiocephalic artery, behind the sterno-clavicular joint. It passes upwards and laterally as a gentle curve behind the scalenus anterior muscle, and at the outer border of the first rib it becomes the axillary artery.The left subclavian artery arises from the arch of the aorta, behind the left common carotid artery. It ascends to the root of the neck and then arches laterally in a manner similar to that of the right subclavian artery The subclavian artery is divided into three parts by the scalenus anterior muscle - the 1st part is medial, the 2nd part posterior, and the 3rd part is lateral to the scalenus anterior.Relations of the First PartAnterior: Immediate relations from medial to lateral side are: (1) Common carotid artery; (2) ansa subclavia; (3) cardiac branches of the vagus and of the sympathetic trunk; (4) vagus; (5) vertebral vein; (6) internal jugular vein; (7) left phrenic nerve; and (8) thoracic duct (on left side only). More superficial relations are: (9) The sternothyroid and the sternohyoid muscles; (10) anterior jugular vein; and (11) sternocleidomastoidPosterior (posterioinferior): (1) Suprapleural membrane; (2) cervical pleura; (3) apex of lung; (4) ansa subclavia; and (5) right recurrent laryngeal nerve.Relations of the Second PartAnterior: (Scalenus anterior. Structures in front of the scalenus anterior are: (2) right phrenic nerve deep to the prevertebral fascia: (3) transverse cervical artery; (4) supracapular artery; (5) subclavian vein; (6) anterior jugular vein; and (7) sternocleidomastoid.Posterior (posteroinferior): (1) Suprapleural membrane; (2) cervical pleura, and (3) apex of lung.Superior: Upper and middle trunks of the brachial plexus.Relations of the Third PartAnterior: (1) Suprascapular vessels; (2) nerve to subclavius (3) prevertebral fascia; (4) subclavian vein; (5) external jugular vein; (6) anterior jugular vein; (7) transverse cervical vein; (8) suprascapular vein; (9) investing fascia; (10) subclavius; (11) middle one-third of the clavicle, and (12) the posterior border of the sternocleidomastoid.Posterior (posteroinferior): (1) Scalenus medius; (2) lower trunk of brachial plexus; (3) suprapleural membrane; (4) cervical pleura; and (5) apex of lung.Superior: (1) Upper and middle trunks of brachial plexus; and (2) inferior belly of omohyoid.Inferior: First rib.
Sternocleidomastoid
Scalenus anterior
Scalenus medius
Omohyoid
Root of Neck