The Anterior Thoracic Nerves (nn. thoracales anteriores) supply the Pectorales major and minor:
The lateral pectoral nerve (lateral anterior thoracic; fasciculus lateralis) the larger of the two, arises from the lateral cord of the brachial plexus, and through it from the fifth, sixth, and seventh cervical nerves. It passes across the axillary artery and vein, pierces the coracoclavicular fascia, and is distributed to the deep surface of the Pectoralis major. It sends a filament to join the medial anterior thoracic and form with it a loop in front of the first part of the axillary artery.
The medial pectoral nerve (medial anterior thoracic; fasciculus medialis) arises from the medial cord of the plexus and through it from the eighth cervical and first thoracic. It passes behind the first part of the axillary artery, curves forward between the axillary artery and vein, and unites in front of the artery with a filament from the lateral nerve. It then enters the deep surface of the Pectoralis minor, where it divides into a number of branches, which supply the muscle. Two or three branches pierce the muscle and end in the Pectoralis major.