Final answer:
The axillary vein is posterior and initially more anterior then medial to the axillary artery, coursing from the union of the basilic and brachial veins to become the subclavian vein. It drains the upper limb and subscapular region.
Step-by-step explanation:
The axillary vein is a major vein in the axillary region that plays a crucial role in draining blood from the upper limb and becomes the subclavian vein. The course and relations of the axillary vein are significant for medical procedures, like the placement of central lines. The axillary vein runs alongside and generally posterior to the axillary artery, though it may start off as more anterior at its inception near the lower margin of the teres major muscle, and becomes more medial as it ascends. It is initially formed by the union of the basilic vein and the brachial veins and lies at the medial side of the axillary artery for most of its extent.The superficial vein of the arm commences as the basilic vein arises from the median antebrachial vein, encounters the median cubital vein, parallels the ulnar vein, and continues into the upper arm. In the upper arm, the vein lies superficially and medially, finally leading to the axillary vein. The axillary vein drains blood not only from the local subscapular region and smaller veins near the scapular region but also receives blood from the entire upper limb before emptying into the subclavian vein as it progresses towards the chest.