MuscleThoracic wall
Internal intercostals
Latin: Mm. intercostales interni
Location: Thorax
View the internal intercostals in 3DOrigin
Costal groove of each rib; fibres run downward and backward (at right angles to the external intercostals).
Insertion
Superior border of the rib below.
Action
Depress the ribs in forced expiration; their interchondral portions assist inspiration.
Nerve supply
Intercostal nerves.
Blood supply
Anterior and posterior intercostal arteries.
Clinical relevance
The neurovascular bundle (vein, artery, nerve from above down) runs between them and the innermost layer — the basis of the safe above-rib chest-drain rule.
Educational anatomy reference, not medical advice. About this content.