Superficial brachial artery crossing over the ulnar and median nerves from posterior to anterior: embryological significance.

A rare variation of the superficial brachial artery was found in the right arm of an 82-year-old male cadaver in student dissection practice. In this case, the axillary artery passed normally between the medial and lateral roots of the median nerve and then bifurcated into a large superficial brachial artery and the deep brachial artery (A. brachialis profunda). The superficial brachial artery passed medially to the ulnar nerve and then crossed over to take a lateral course to the median nerve at the midpoint of the upper arm. It finally divided into the radial and ulnar arteries at the cubital fossa. The deep brachial artery terminated as the inferior ulnar collateral artery. These findings indicate that the present variant was a well-developed medial type of the superficial brachial artery that gave off the ulnar and radial arteries. The anatomical and embryological significance of the findings are discussed.