Muscles of the Thorax

The muscles of the thorax include both the diaphragm as well as the muscles of the thoracic cage.

The diaphragm can be located below the lungs and consists of a sheet of skeletal muscle which displays a double-domed structure. The diaphragm is important as it separates the thoracic cavity from the abdominal cavity and therefore requires 3 openings that act as channels for structures to pass through from the thorax and into the abdomen. Examples of structures which require these channels are the oesophagus, aorta and inferior vena cava. The diaphragm is also considered the primary muscle of respiration as it can change shape to alter the volume of the thoracic cavity to allow for respiration. The phrenic nerve provides the motor innervation to the diaphragm whilst the inferior phrenic arteries provide the majority of the arterial bloody supply.

The intercostals (external, internal and innermost), subcostals and transversus thoracic are the 5 muscles which comprise the thoracic cage and are therefore considered muscles of the thorax. Together, these muscles alter the volume of the thoracic cavity through moving the rib cage appropriately during respiration.


In this section, learn more about the muscles of the thorax–  the diaphragm and the muscles of the thoracic cage.

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The Diaphragm

The Muscles of the Thoracic Cage


Anatomical Areas

The Quadrangular Space

by Oliver Jones


Extensor Hallucis Longus

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