Ventral Branches of Thoracic Nerves
There are 12 pairs of ventral rami of the thoracic nerves , which do not constitute plexuses. Almost all 12 are situated between the ribs (intercostal nerves), with the twelfth lying below the last rib (subcostal nerve). Intercostal nerves are distributed to the walls of the chest and abdomen. The communicating branches join the intercostal nerves posteriorly in the intercostal spaces.
Most of the fibers of the ventral branch of T1 enter the constitution of the brachial plexus, but the rest form the first intercostal nerve. The ventral branch of T2 sends an anastomotic branch to the brachial plexus, however, most of its fibers constitute the second intercostal nerve.
The last ventral branch of the thoracic nerves (T12) is called the subcostal nerve because it is located below the 12th rib.
The intercostal nerves run along the inner surface, along the lower border of the corresponding rib, occupying the costal groove, parallel to and below the intercostal vein and artery.
The sensory fibers are dispersed through the lateral and anterior regions of the thorax, called, respectively, the lateral cutaneous branch and the anterior cutaneous branch.
From the 7th to 12th thoracic branches, anteriorly, they leave the ribs to invade the abdomen, thus innervating the muscles and the skin to a plane that mediates the umbilicus and pubic symphysis.
The subcostal nerve (T12) gives an anastomotic branch to the lumbar plexus, and on the other hand, some of its sensory fibers go to the gluteal region and lateral aspect of the thigh.
| NERVES OF THE ANTERIOR ABDOMINAL WALL|
|Source: NETTER, Frank H.. Atlas of Human Anatomy. 2nd edition Porto Alegre: Artmed, 2000.|
| TYPICAL THORACIC SPINAL NERVE|
Source: NETTER, Frank H.. Atlas of Human Anatomy. 2nd edition Porto Alegre: Artmed, 2000.