External intercostal muscles
Musculi intercostales externi
MuscularDeep musclesWhole bodyLeft and right
View left in 3D View right in 3D
- What it is
- Eleven thin sheets, one in each intercostal space, whose fibres run from the lower border of one rib down and forwards to the upper border of the rib below; they reach from the rib tubercles to the costochondral junctions, beyond which the external intercostal membrane continues.
- Function
- Raise the ribs in inspiration and stop the intercostal spaces bulging or being sucked in.
- Size
- Each space ~1.5–2 cm tall; sheets ~3 mm thick.
- Clinical note
- The intercostal nerve and vessels run under the rib above, so chest drains and needles are passed just over the upper border of a rib.