Muscles There are 3
muscular layers in each intercostal space, consisting of the
external intercostal muscle, the
internal intercostal muscle, and the thinner
innermost intercostal muscle. These muscles help to move the ribs during
breathing.
Neurovascular bundles Neurovascular bundles are located between the internal intercostal muscle and the innermost intercostal muscle. The
neurovascular bundle has a strict order of
vein-
artery-
nerve (VAN), from top to bottom. This neurovascular bundle runs high in the intercostal space, and the smaller collateral neurovascular bundle runs just superior to the lower rib of the space (in the order NAV from superior to inferior). Invasive procedures such as
thoracentesis are performed with oblique entry of the instrument, directly above the upper margin of the relevant rib, to avoid damaging the neurovascular bundles.
Nerves In reference to the muscles of the
thoracic wall, the intercostal nerves and vessels run posterior to the internal intercostal muscles: therefore, they are generally covered on the inside by the parietal
pleura, except when they are covered by the innermost intercostal muscles, innermost intercostal membrane,
subcostal muscles or the
transversus thoracis muscle. == References ==