trunci plexus brachialis

[TA] trunks of brachial plexus: the three trunks (superior, middle, and inferior) of the brachial plexus, arising from the anterior branches of the lower four cervical nerves and the first thoracic nerve near the lateral border of the scalenus anterior muscle; they continue laterally and downward, above and behind the subclavian artery, and near the clavicle each splits into an anterior and a posterior division. The anterior divisions of the superior and medial trunks unite to form the lateral fasciculus and that of the inferior trunk forms the medial fasciculus of the plexus; and the posterior divisions of the three trunks form the posterior fasciculus of the plexus.