The posterior circumflex humeral artery is situated around the shoulder and upper chest. It branches off from the axillary artery, which supplies oxygenated blood to the armpit, upper arm, and thorax before winding down and becoming part of the brachial artery. The artery connects to the axillary artery at the subscapularis, which is a muscle found at the top of the shoulder and humerus. Once the posterior circumflex humeral artery branches off from the axillary artery, it distributes oxygenated blood to the shoulder joint and deltoid, a large triangular shaped muscle found at the top of the shoulder-joint. The artery pumps fresh blood into the muscle, making the joint flexible and healthy.