Trunk (thorax, abdomen, back)

External Intercostal Muscles

Musculi intercostales externi

Origin

Lower border of a rib (1st through 11th)

Insertion

Upper border of the rib below

Function

Elevation of the ribs during inspiration

Innervation

Intercostal nerves (T1-T11)

Movement & chain

Works together with the diaphragm during inspiration by enlarging the thoracic cavity; fibers run obliquely from cranio-lateral to caudo-medial.

Palpation

Palpable within the intercostal spaces along the anterolateral chest wall between adjacent ribs.

Clinical

Key muscles for active inspiration by elevating the ribs (bucket-handle mechanism); painful intercostal muscle strains from severe coughing or twisting.

Segmental innervation

Intercostal nerves, segmental per space, T1-T11.

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)