Pectoral chest region anatomy

The lateral and medial pectoral nerves arise from the cords of the brachial plexus and innervate the pectoral major and minor muscles. The lateral pectoral nerve  courses along the undersurface of the pectoralis major muscle, in the fascial plane between the pectoralis major and minor muscles. The medial pectoral nerve also runs between the pectoralis major and minor muscles.
The intercostobrachial nerve, the lateral cutaneous branches of the thoracic intercostal nerves, the long thoracic nerve, and the thoracodorsal nerve run in variable anatomic courses, piercing the fascial plane between the serratus anterior muscle, ribs, and pectoralis minor muscle. These nerves innervate deep structures in the anterior, posterior, and lateral breast; the chest wall; axillary structures; and the upper abdomen.