How Blood and Lymph Flow Through the Shoulder
The tissues of the pectoral girdle need oxygen. So a complex series of arteries supplies blood flow through the shoulder, upper arm and chest area. And because the axilla includes several important lymph nodes, that lymph has to flow.
Arterial blood flow is provided by branches of the subclavian artery and the axillary artery that runs from the axilla and continues down into the arm as the brachial artery.
Internal thoracic: This artery starts on the first part of the subclavian artery and descends anteriorly and medially. It runs posterior to the clavicle and 1st costal cartilage and forms branches in the thoracic cage.
Suprascapular: This artery stems from the thyrocervical trunk (a branch of the subclavian artery) and runs inferiorly and laterally across the anterior scalene muscle, phrenic nerve, subclavian artery, and brachial plexus. Next, it runs posterior and parallel to the clavicle and then laterally to the infraspinous fossa of the scapula.
Superior thoracic: This artery starts on the first part of the axillary artery and runs anteriorly and medially along the superior edge of the pectoralis minor and then to the thoracic wall.
Thoracoacromial: This artery starts on the second part of the axillary artery and curls around the superomedial edge of the pectoralis minor before dividing into four branches: the pectoral, deltoid, acromial, and clavicular branches.
Lateral thoracic: This artery also starts on the second part of the axillary artery and descends onto the thoracic wall.
Circumflex humeral: This artery has two parts (anterior and posterior) that branch off the third part of the axillary artery and anastomose to encircle the surgical neck of the humerus.
Subscapular: This artery also starts on the third part of the axillary artery and descends along the lateral border of the scapula and divides into the circumflex scapular artery and the thoracodorsal artery:
Circumflex scapular: This branch curves around the lateral border of the scapula and enters the infraspinous fossa before anastomosing with the suprascapular artery.
Thoracodorsal: This branch descends into the latissimus dorsi muscle.
Deep brachial artery of the arm: This artery starts on the brachial artery and runs along the radial groove of the humerus to the elbow joint.
Superior ulnar collateral: This artery also starts on the brachial artery and runs to the posterior part of the elbow.
Inferior ulnar collateral: This artery starts on the brachial artery and runs to the medial part of the elbow.
Venous drainage is provided by deep veins that travel alongside the arteries and by two superficial veins, the cephalic vein and the brachial vein.
The lymphatic vessels
The deltopectoral nodes are superficial lymph nodes that receive lymph from superficial vessels. The axilla contains five groups of lymph nodes:
Pectoral (anterior) nodes: This group of nodes is located on the medial wall of the axilla and at the bottom of the pectoralis minor. Lymph from the anterior thoracic wall and breast flows into these nodes.
Subscapular (posterior) nodes: These nodes lie along the posterior axillary fold. They get lymph from the posterior thoracic wall and scapular area.
Humeral (lateral) nodes: This group is on the lateral wall of the axilla near the axillary vein. Most of the lymph from the upper extremity flows into these nodes.
Central nodes: These nodes lie underneath the pectoralis minor. Lymph from the pectoral, subscapular, and humeral nodes flow into the central nodes.
Apical nodes: These nodes are near the apex of the axilla. They get lymph from the other axillary nodes.
The vessels leaving the apical nodes form the subclavian lymphatic trunk, which leads to the right lymphatic duct or the thoracic duct on the left side.
The axillary nodes are also the most common site for the metastasis, or the spreading, of breast cancer cells. Sentinel nodes is the name given to the first lymph nodes into which the tumor drains. With breast cancer, these sentinal nodes are usually the axillary nodes. A biopsy may be performed on these nodes to determine if cancer is spreading. If the biopsy is negative, metastasis is unlikely; if the biopsy is positive, the cancer cells may have spread into more lymph nodes beyond the sentinel nodes.