| Nerve: Intercostal nerves | |
|---|---|
| Diagram of the course and branches of a typical intercostal nerve. | |
| Intercostal nerves, the superficial muscles having been removed. | |
| Latin | nervi intercostales |
| Gray's | subject #211 945 |
| Innervates | intercostal muscle |
| From | thoracic nerves (T1-T11) |
| MeSH | Intercostal+Nerves |
The intercostal nerves are the anterior divisions (rami anteriores; ventral divisions) of the thoracic spinal nerves from T1 to T11.
Each nerve is connected with the adjoining ganglion of the sympathetic trunk by a gray and a white ramus communicans. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum and differ from the anterior divisions of the other spinal nerves in that each pursues an independent course without plexus formation.
The first two nerves supply fibers to the upper limb in addition to their thoracic branches; the next four are limited in their distribution to the parietes of the thorax; the lower five supply the parietes of the thorax and abdomen. The 7th intercostal nerve terminates at the xyphoid process, at the lower end of the sternum. The 10th intercostal nerve terminates at the umbilicus. The twelfth (subcostal) thoracic is distributed to the abdominal wall and groin.
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The anterior division of the first thoracic nerve divides into two branches: one, the larger, leaves the thorax in front of the neck of the first rib, and enters the brachial plexus; the other and smaller branch, the first intercostal nerve, runs along the first intercostal space, and ends on the front of the chest as the first anterior cutaneous branch of the thorax.
Occasionally this anterior cutaneous branch is missing.
The first intercostal nerve rarely gives off a lateral cutaneous branch; but sometimes sends a small branch to communicate with the intercostobrachial.
From the second thoracic nerve it frequently receives a connecting twig, which ascends over the neck of the second rib. This nerve was first described by Kuntz in 1927. There is considerable anatomic variation, but Kuntz nerve may be present in 40-80% of the population.[1], [2]
The anterior divisions of the second, third, fourth, fifth, and sixth thoracic nerves, and the small branch from the first thoracic, are confined to the parietes of the thorax, and are named thoracic intercostal nerves.
They pass forward in the intercostal spaces below the intercostal vessels. At the back of the chest they lie between the pleura and the posterior intercostal membranes, but soon pierce the latter and run between the two planes of Intercostal muscles as far as the middle of the rib.
They then enter the substance of the Intercostales interni, and, running amidst their fibers as far as the costal cartilages, they gain the inner surfaces of the muscles and lie between them and the pleura.
Near the sternum, they cross in front of the internal mammary artery and Transversus thoracis muscle, pierce the Intercostales interni, the anterior intercostal membranes, and Pectoralis major, and supply the integument of the front of the thorax and over the mamma, forming the anterior cutaneous branches of the thorax; the branch from the second nerve unites with the anterior supraclavicular nerves of the cervical plexus.
Numerous slender muscular filaments supply the Intercostales, the Subcostales, the Levatores costarum, the Serratus posterior superior, and the Transversus thoracis. At the front of the thorax some of these branches cross the costal cartilages from one intercostal space to another.
The lateral cutaneous branch of the second intercostal nerve does not divide, like the others, into an anterior and a posterior branch; it is named the intercostobrachial nerve.
The lateral cutaneous branch of the last thoracic nerve is large, and does not divide into an anterior and a posterior branch.
It perforates the Obliqui internus and externus, descends over the iliac crest in front of the lateral cutaneous branch of the iliohypogastric, and is distributed to the skin of the front part of the gluteal region, some of its filaments extending as low as the greater trochanter.
This article was originally based on an entry from a public domain edition of Gray's Anatomy. As such, some of the information contained within it may be outdated.
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