Description
The thoracic nerves refer to twelve pairs of spinal nerves that emerge from the intervertebral foramina of the twelve thoracic vertebrae, i.e., inferior to their corresponding numerical thoracic vertebrae. The twelfth thoracic nerve is referred to as the subcostal nerve as it courses below the twelfth rib.
The thoracic nerves are highly segmental. Posterior (dorsal) sensory roots and anterior (ventral) motor roots merge to form the thoracic nerves, which quickly branch into posterior (dorsal) and anterior (ventral) rami. The posterior rami run dorsally, innervating the axial back muscles and skin overlying the back. The anterior rami run in an anterolateral direction between the ribs. The major branch is located in a neurovascular bundle just inferior to the preceding rib, for example, the anterior ramus of the sixth thoracic nerve runs under the inferior surface of the sixth rib, between the internal and innermost intercostal muscles.
The subcostal nerve (or anterior ramus of the twelfth thoracic nerve) runs inferior to the twelfth rib. It gives off a branch to the iliohypogastric nerve and is often discussed together with the lumbar plexus. The bulk of this nerve continues laterally, across the anterior surface of the quadratus lumborum muscle. It then penetrates transversus abdominis muscle and runs between it and the internal abdominal oblique muscle.
Related parts of the anatomy
