The intercostal space (ICS) is the anatomic space between two ribs (Lat. costa). Since there are 12 ribs on each side, there are 11 intercostal spaces, each numbered for the rib superior to it.
Intercostal spaces, viewed from the left.
Sternocostal and interchondral articulations. Anterior view.
Structures in intercostal space
Order of components
Comprehensive insight in the anatomy of the intercostal spaces is mandatory for everyone who practices medicine. One particular concept is that the neurovascular bundle has a strict order: V-A-N, or vein-artery-nerve, from top to bottom (as illustrated). This neurovascular bundle runs high in the intercostal space, and the collateral neurovascular bundle runs just superior to the inferior rib of the space (in the order N-A-V from superior to inferior). Invasive procedures such as thoracentesis are thus performed with oblique entry of the instrument, directly above the upper margin of the relevant rib.
In reference to the muscles of the thoracic wall, the intercostal nerves and vessels run just behind 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.
- Troyer, A. D., Kelly, S., Macklem, P. T., & Zin, W. A. (1985). Mechanics of intercostal space and actions of external and internal intercostal muscles. Journal of Clinical Investigation, 75(3), 850-857. doi:10.1172/jci111782
- Anatomy figure: 18:04-00 at Human Anatomy Online, SUNY Downstate Medical Center - "Structural organization within an intercostal space."
- Anatomy photo:18:01-0108 at the SUNY Downstate Medical Center - "Thoracic Wall: The Anterior Thoracic Wall"