The spaces between the ribs.
|Search for Intercostal space in Gray's.|
From the outside in:
In the superior part of each intercostal space, behind the lower border of the rib above (in the costal groove), between internal intercostal muscle and transversus thoracis lies the neurovascular bundles. This consists of (from the top down (i.e.VAN))
Clinically this is important as insertion of any instrument between the ribs (e.g. needle for aspiration) should be aimed at passing just over the upper border of the rib below to avoid hitting this bundle (risk of pain and haemothorax).