[TA] continuation of the anterior rami of spinal nerves (intercostal nerves) T1-T6 distal to the origin of the lateral cutaneous branches; they become cutaneous in the parasternal line and divide into medial (sternal) and lateral (medial mammary) branches; distributed to anterior thoracic wall. SYN: ramus cutaneus anterior pectoralis nervi intercostalis [TA], pectoral anterior cutaneous branch of intercostal nerves.