Muscles of the thoracic wall

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Muscles of the thoracic wall

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Muscles of the Thoracic Wall

Figure 1. A Posterior view and B antero-lateral view of muscles of the thoracic wall.
Figure 2. Antero-lateral view of A subcostal muscles (anterior portion of sternum and ribs dissected out), and B transversus thoracis muscle.
Figure 3. Tissue cross section of two ribs and associated tissues. B Antero-lateral view of ribs and most superficial fascia.
Figure 4. Movement of ribcage and muscles of the thoracic wall during inhalation and exhalation.
Proximal Attachment
Distal Attachment
Serratus posterior superior
  • Nuchal ligament & spinous processes of C7-T3 vertebrae
  • Superior borders of ribs 2-4
  • Ventral rami of intercostal nerves of T1-T5
  • Elevation of superior 4 ribs during inspiration
  • Role in proprioception
Serratus posterior inferior
  • Spinous processes of T11-L2 vertebrae
  • Inferior border of ribs 8-12
  • Ventral rami of intercostal nerves of T9-T12
  • Depressing inferior ribs
  • Role in proprioception
Levatores costarum
  • Transverse processes of C7-T11 vertebrae
  • Subjacent ribs between tubercle & angle
  • Lateral branch of posterior rami of thoracic spinal nerves
  • Elevate ribs
External intercostals
  • Inferior border of ribs above 
  • From tubercles of ribs posteriorly to costochondral junctions anteriorly
  • Superior border of rib below
  • Intercostal nerves traveling in respective intercostal space
  • Elevate ribs during forced inspiration
Internal intercostals
  • Inferior border of ribs above
  • From bodies of ribs & costal cartilages to sternum anteriorly & angles of ribs posteriorly
  • Superior border of rib below
  • Play a role during expiration
Innermost intercostals
  • Inferior border of ribs above
  • Deep to internal intercostals
  • Superior border of rib below
  • Play a role during expiration
  • Internal surface of lower ribs near angles
  • Superior border of 2nd-3rd rib
  • Intercostal nerves
  • Play a role during expiration
Transversus thoracis
  • Posterior surface of lower sternum
  • Internal surface of costal cartilages 2-6
  • Intercostal nerves
  • Slightly depress ribs during expiration
  • Might provide proprioceptive information


The thoracic wall surrounds the thoracic cavity, which is the anatomical region where viscera like the heart and lungs can be found.

The thoracic wall contains a variety of muscles, where many of the muscles that cover and attach to the thoracic wall have a primary action elsewhere, such as the arms, neck, and abdomen, and it is their secondary actions that affect the movements of the thoracic wall.

For example, the pectoralis major and pectoralis minor muscles overlay the thoracic wall but they are primarily involved with movements of the upper limb and their secondary action is to act on the thoracic wall as accessory muscles of respiration.

However, the thoracic wall also does have muscles that have their primary action in the thoracic wall, and these are called the true muscles. They are the serratus posterior, levatores costarum, subcostals, transversus thoracis, and the innermost, internal, and external intercostals.

Let’s start with the two serratus posterior muscles. There’s a serratus posterior superior muscle and serratus posterior inferior muscle on each side. The Serratus posterior superior muscles have their proximal attachment at the nuchal ligament and the spinous processes of C7 through T3 vertebrae and their distal attachment at the superior borders of the 2nd through 5th ribs. Its main action is the elevation of the superior 4 ribs during inspiration.

The serratus posterior inferior muscles have their proximal attachment at the spinous processes of T11 through L2 vertebrae and their distal attachment at the inferior borders of 9th through 12th ribs near their angles. Its main action is depressing the inferior ribs in order to prevent them from being pulled upwards by the diaphragm.

Both of these muscles have also been shown to have a role in proprioception, meaning that they might make you aware of the position of the body. For example, when you’re lying in bed with your eyes closed, these muscles, among others, could send signals to the brain regarding where you are and what’s your position in relation to the bed.


  1. "Clinically oriented anatomy" Philadelphia: Wolters Kluwer/Lippincott Williams & Wilkins Health (2014)
  2. "Dermatomes and dogma" Practical neurology 11.2 (2011)
  3. "Conflicting dermatome maps: educational and clinical implications." Journal of Orthopaedic & Sports Physical Therapy 41.6 (2011)

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