Axillary Artery Branches
The axillary artery, the continuation of the subclavian artery at the first rib, crosses the axilla in three parts defined by the pectoralis minor muscle. Each part gives a predictable number of branches — one, two, and three respectively.
✦ The Mnemonic
"Send The Lateral Squad: Anteriorly, Posteriorly"
Six branches: 1 (part 1), 2 (part 2), 3 (part 3) — a 1-2-3 pattern
Clinical Breakdown
The memory aid for counting branches is 1-2-3: part 1 gives 1 branch, part 2 gives 2, part 3 gives 3. The axillary artery becomes the brachial artery at the lower border of teres major. The pectoralis minor is the key landmark — it crosses the artery superficially and divides it into three parts.
The subscapular artery is the largest branch, arising 4 cm distal to the axillary margin. It rapidly divides into the circumflex scapular artery (passes through the triangular space — borders: long head triceps, teres major, teres minor) and the thoracodorsal artery (accompanies the thoracodorsal nerve to latissimus dorsi, important in breast reconstruction flaps).
The posterior circumflex humeral artery accompanies the axillary nerve through the quadrilateral space (bordered by: subscapularis/teres minor above, teres major below, long head triceps medially, surgical neck of humerus laterally). Fractures of the surgical neck of humerus can damage both the axillary nerve and this artery simultaneously.
⭐ Clinical Pearl
Thoracodorsal artery — the vascular pedicle of the latissimus dorsi myocutaneous flap, the workhorse of breast reconstruction after mastectomy. Its reliable anatomy (from the subscapular axis) makes it a preferred reconstructive option. The thoracodorsal nerve runs with it and must be preserved to maintain muscle function if the flap is used as a functional transfer.