[Location] With the elbow flexed, on the medial aspect of the elbow, in the depression between the olecranon of the ulna and the medial epicondyle of the humerus. (Fig.26)
 
[Regional Anatomy] Skin→subcutaneous tissue→the groove of the ulnar nerve. Superficial layer. the medial branchial cutaneous nerve, the medial antebrachial cutaneous nerve, the subordinatial branches of the basilis vein; deep layer, the ulnar nerve in the groove of it, the arterial and venous network formed by the superior ulnar collateral arteries and veins, and the ulnar recurrent arteries and veins.