Brachial plexus gather more information to evaluate the anatomy more. Brachial plexus The brachial plexus is a network of nerves formed by the ventral rami of the lower four cervical nerves and first thoracic nerve (C5, C6, C7, C8, and T1). This plexus extends from the spinal cord, through the cervicoaxillary canal in the neck, over the first rib, and into the armpit. It supplies afferent and efferent nerve fibers to the chest, shoulder, arm and hand. The brachial plexus is divided into five "roots", three "trunks", six "divisions" (three anterior and three posterior), three "cords", and five "branches". There are five
Perforating branches of internal thoracic artery Perforating branches of internal thoracic artery The perforating branches of the internal thoracic artery pierce through the internal intercostal muscles of the superior six intercostal spaces. These small arteries run with the anterior cutaneous branches of the intercostal nerves. The perforating arteries constitute part of the blood supply to the pectoralis major and the overlying tissue and skin. The second, third and fourth perforating branches give off medial mammary branches, which become enlarged during lactation. Chung, Kyung Wong, Ph.D. "Board Review Series: Gross Anatomy, 3rd ed. 114-115. Williams and Wilkins: 1995." Lockhart, R.D., et al. "Anatomy of the Human Body."