Answer:
The principal blood supply arises from one or two large perforating arteries from the second or third intercostal space located lateral to the sternum. The flap's axial arteries run just above the pectoralis fascia in a medial to lateral direction towards the shoulder. Collateral connections are formed laterally with the thoracoacromial perforators over the coracoid process of the shoulder. The flap can potentially extend from the sternum laterally to the anterior shoulder. Because of additional collaterals with perforators from the deltoid muscle, extension of the flap to the upper arm is also possible though a delay may be needed. The upper margin of the flap is usually defined by the clavicle and acromion while the parallel lower margin is usually designed to spare the nipple and extend toward the anterior axillary fold. The flap can be rotated to cover chest wall defects of the lower thorax or opposite side. It has also been rotated upwards for use in head and neck reconstruction.