"Muscular branches from the intercostal nerves of the respective intercostal space (T1-T11), which run with the intercostal vessels under the costal groove in between the internal and innermost intercostal muscles."
Expected headings
"Blood supply"
"Action"
"The internal intercostal muscles are the middle muscle of the three intercostal muscles and arise from the costal groove of the rib above. The fibres run in a downwards, backwards and lateral direction (perpendicular to the external intercostal muscles) and insert into the superior border of the rib below. Anteriorly, the lower muscles become continuous with the internal oblique muscles in the anterolateral abdominal wall. As their name indicates, they are internal to the external intercostal muscles."