Internal intercostal muscles
Musculi intercostales interni
MuscularDeep musclesWhole bodyLeft and right
View left in 3D View right in 3D
- What it is
- Eleven thin sheets deep to the external intercostals with fibres at right angles to them (down and backwards), from the sternum and costal cartilages back to the angles of the ribs, where the internal intercostal membrane takes over.
- Function
- Pull the ribs down in forced expiration; their front (interchondral) parts help raise the ribs in inspiration.
- Size
- Each space ~1.5–2 cm tall; sheets 2–3 mm thick.
- Clinical note
- The intercostal neurovascular bundle runs in the costal groove between this layer and the innermost intercostals.