The arterial blood supply of the breast has medial and lateral vascular components; it is supplied with blood by the internal mammary artery (from the medial aspect), the lateral thoracic artery (from the lateral aspect), and the 3rd, 4th, 5th, 6th, and 7th intercostal perforating arteries. Drainage of venous blood from the breast is by the superficial vein system under the dermis, and by the deep vein system parallel to the artery system. The primary lymph drainage system is the retromammary lymph plexus in the pectoral fascia.