Intercostal nerves

Intercostal nerves
Diagram of the course and branches of a typical intercostal nerve.
Intercostal nerves, the superficial muscles having been removed.
Details
From	thoracic nerves (T1-T11)
Innervates	intercostal muscle
Identifiers
Latin	nervi intercostales
MeSH	A08.800.800.720.800.350
Dorlands /Elsevier	n_05/12565929
TA	A14.2.04.006
FMA	75467
Anatomical terms of neuroanatomy []

The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum and differ from the anterior rami 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 walls of the thorax; the lower five supply the walls 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 navel. The twelfth (subcostal) thoracic is distributed to the abdominal wall and groin.

Unlike the nerves from the autonomic nervous system that innervate the visceral pleura of the thoracic cavity, the intercostal nerves arise from the somatic nervous system. This enables them to control the contraction of muscles, as well as provide specific sensory information regarding the skin and parietal pleura. This explains why damage to the internal wall of the thoracic cavity can be felt as a sharp pain localized in the injured region. Damage to the visceral pleura is experienced as an un-localized ache.

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.