Innermost intercostal mm.

The innermost intercostal mm. are a thin layer of muscular and tendinous fibers situated upon the inner surface of the chest wall laterally. Anteriorly and posteriorly, the innermost intercostal mm. are membranous. The innermost intercostal mm. are in the same layer as the subcostal mm. (posteriorly) and the transversus thoracis mm. (anteriorly).

The innermost intercostal mm. have the same fiber orientation as the internal intercostal mm. The intercostal neurovascular bundles lie between the innermost and internal intercostal mm.