The intercostal nerves run in the intercostal spaces sandwiched between the socalled innermost intercostal muscle and the internal and external intercostal muscles superficially joined by the intercostal arteries and veins
The lateral cutaneous branches of the intercostal nerves branch off in the midaxillary line, pierce the internal and external intercostal muscles and branch into a posterior and an anterior terminal branch; the latter runs anterior to innervate the skin covering the infero-lateral part of the breast
The anterior cutaneous branches of the intercostal nerves run anterior to the internal mammary artery, pierce the intercostal membranes and innervate the medial part of the breast
