Anterior Rami of Thoracic Nerves (Left)

Description

The anterior rami of the thoracic nerves are ventral branches of the T1- T12 spinal nerves. They are one of the two terminal branches of these spinal nerves, the other being the posterior (dorsal) rami.

The anterior ramus of the first thoracic nerve is considered a part of the brachial plexus where it combines with the anterior ramus of the eighth cervical nerve to form the lower trunk of the brachial plexus. Fibers from the anterior ramus of the first thoracic nerve contribute to the median, medial pectoral, medial antebrachial cutaneous, medial brachial cutaneous, ulnar, and radial nerves. Additional fibers of the anterior ramus of the first thoracic nerve run below the first rib and supply innervation to the corresponding thoracic skin and muscles. This is the first intercostal nerve.

The anterior rami of the second through twelfth thoracic nerves are segmental in nature and travel just inferior to the corresponding rib. The anterior rami of thoracic nerves that run between the inner intercostal muscle and the innermost intercostal muscles are called intercostal nerves except for the anterior rami of the twelfth thoracic spinal nerve. This is generally called the subcostal nerve as it runs below the lowest rib.

The anterior rami of the second and third thoracic nerves can send some fibers to the medial cord as intercostobrachial nerves. However, neither ramus is considered a part of the brachial plexus.

The anterior rami of the fourth through sixth thoracic nerves supply the skin and muscles of the thorax, while the anterior rami of the seventh through eleventh thoracic spinal nerves supply the skin and muscles of the thorax and abdomen.

The anterior ramus of the twelfth thoracic nerve, the subcostal nerve, serves the abdominal skin and musculature. Additionally, it can communicate with fibers of the lumbar plexus, specifically the iliohypogastric nerve.