Trunk (thorax, abdomen, back)

Innermost Intercostal Muscles

Musculi intercostales intimi

Origin

Inner surface of a rib (2nd through 11th), deep to the internal intercostals

Insertion

Inner surface of the rib below

Function

Assists the internal intercostals in expiration; stabilizes the intercostal space

Innervation

Intercostal nerves

Movement & chain

Runs in the same direction as the internal intercostals but is not always functionally sharply distinguishable from them; often regarded as a functional unit with transversus thoracis.

Palpation

Deep on the inner surface of the ribs separated from internal intercostals by the intercostal neurovascular bundle; not palpable.

Clinical

House the intercostal vein, artery, and nerve (VAN) in the subcostal groove; essential landmark for safe chest tube insertion and intercostal nerve blocks.

Segmental innervation

Intercostal nerves, segmental per space.

In clinical practice

Ergonomic patient repositioning (log-roll technique in spinal trauma) and pressure offloading; maintain neutral spinal alignment in bedridden patients.

Region in the model

Trunk (thorax, abdomen, back)