(Intercostal Nerves): These travel along the costal grooves of the ribs to supply intercostal muscles, the chest wall, and the skin of the thorax. T12cap T 12
| Landmark | Corresponding Thoracic Nerve | | :--- | :--- | | Supraclavicular fossa | C3–C4 (not thoracic) | | Apex of axilla | T1–T2 | | Sternal angle (manubriosternal) | T2 | | Nipple (4th intercostal space) | | | Xiphoid process | T6 | | Costal margin | T7 | | Umbilicus | T10 | | Pubic symphysis / inguinal ligament | T12 / L1 | thoracic nerve distribution
The larger branch that becomes the intercostal nerves (T1–T11) or the subcostal nerve (T12). (Intercostal Nerves): These travel along the costal grooves
| Nerve | Region | Key Motor Targets | Key Sensory (Dermatome) | | :--- | :--- | :--- | :--- | | | Superior thorax | Intercostals, hand muscles (via T1 contribution to brachial plexus) | Medial forearm/axilla | | T2 | 1st-2nd intercostal space | Intercostals | Upper chest, axilla (intercostobrachial nerve) | | T3-T6 | Upper thorax | External/internal intercostals | Anterior chest wall (nipple = T4) | | T7-T9 | Mid-lower thorax | Intercostals, serratus posterior inferior | Epigastrium (xiphoid = T6) | | T10 | Subcostal region | Abdominal obliques, transversus abdominis | Umbilicus (landmark) | | T11-T12 | Lower thorax/flank | Abdominal muscles, quadratus lumborum | Hypogastrium, inguinal region | the chest wall