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Chest wall

Last updated: March 30, 2021

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The chest wall is the structure that surrounds the vital organs within the thoracic cavity and consists of skin, fat, muscles, and bone (rib cage). It furthermore supports breathing and stabilizes the shoulder girdle and upper arms during movement. Anatomical landmarks that play an important role in clinical examination and thoracic surgery include the midsternal line, the midclavicular line, and the midaxillary line. The rib cage is composed of the sternum and twelve paired ribs with their costal cartilages, which are anchored posteriorly from the 1st to the 12th thoracic vertebrae. Muscles that comprise the chest wall include the external, the internal and innermost intercostal muscles, the subcostal muscles, and the transverse thoracic muscles, all of which are innervated by the intercostal nerves. These muscles are involved in the movement of the rib cage during inspiration and expiration. There are also muscles that attach to the chest wall but are not inherently part of it (e.g., pectoralis major, serratus anterior, latissimus dorsi), which help with respiration and upper limb movement. The neurovascular bundle (intercostal artery, vein, and nerve) runs along the inferior surface of the rib within the costal groove. To prevent injury of the intercostal nerves and vessels during surgery, chest tubes are, therefore, placed close to the upper margin of a rib. Conditions that affect the chest wall include costochondritis, pectus excavatum, and thoracic outlet syndrome.

The chest wall is composed of the thoracic skin, fat, muscles, and skeleton .

Below each rib parks a VAN: Vein, Artery, Nerve (intercostal bundles from superior to inferior).

Chest tubes are placed along the upper margin of a rib to prevent injury of the intercostal nerves and vessels, which run along the lower margin.

The thorax is bounded by 12 sets of ribs that wrap around from the T1–T12 vertebrae of the thoracic spine and connect to the sternum and/or costal cartilages.

Sternum

  • Composed of 3 flat bones
    • Manubrium: cartilages of 1st ribs articulate here
    • Sternal body: cartilages of 3rd–7th ribs attach here
    • Xiphoid process: small cartilaginous extension at the 7th dermatome that ossifies in adults
  • Suprasternal notch: visible and palpable U-shaped depression above the manubrium between the two clavicles
  • Sternal angle

Ribs

There are 12 pairs of ribs separated by intercostal spaces (ICSs)

  • Parts of a typical rib
    • Head of the rib
    • Tubercle of the rib: Small bump near the head on the posterior rib surface.
    • Body of the rib (shaft)
  • Types
    • True ribs (ribs 1–7): Connect directly to the sternum via costal cartilage.
    • False ribs (ribs 8–10): Connect indirectly to the sternum via the costal arch.
    • Floating ribs (ribs 11–12): Do not connect to the sternum.
    • Accessory ribs: Anatomical variant in up to 0.5% of the population that usually arises from the seventh cervical vertebra (cervical rib).
  • Articulations

Intercostal surface projections

The first rib is not palpable because the clavicle overlies it. When counting the ribs, one starts at the palpable manubriosternal junction (sternal angle), where the second rib attaches.

A cervical rib is usually asymptomatic but can cause compression of the C8/T1 roots, the lower trunk of the brachial plexus, and/or the subclavian artery (thoracic outlet syndrome).

References:[1]

The chest wall is comprised of 5 muscles, which are all innervated by the intercostal nerves:

Overview of chest wall muscles
Course Function
Intercostal muscles (found between the ribs) External intercostal muscles Run anteroinferiorly Elevate the ribs during inspiration (widens ICSs → ↑ thoracic volume)
Internal intercostal muscles Run posteroinferiorly Lower the ribs during expiration (narrows ICSs → ↓ thoracic volume)
Innermost intercostal muscles Run posteroinferiorly Lower the ribs during expiration (narrows ICSs → ↓ thoracic volume)
Subcostal muscles Run posteroinferiorly
Transversus thoracis muscle Runs craniolaterally from posterior surface of lower sternum to cartilage of 2nd–6th ribs

Overview of other muscles that attach to the thoracic wall
Muscles Origin Insertion Innervation Function
Pectoralis major muscle
  • Flexes, adducts and medially rotates the arm
  • Accessory muscle of respiration
Pectoralis minor muscle
  • Ribs 3–5 near costal cartilages
  • Stabilization of the scapula
  • Accessory muscle of respiration
Serratus anterior muscle
  • Upper borders of ribs 1–8
  • Scapula: protraction
  • Inferior angle of the scapula: upward rotation
  • Maintains position of the medial border and inferior angle of the scapula in contact with the thoracic wall
  • Abduction of the arm (> 100°)
  • Accessory muscle of respiration
Subclavius muscle
Latissimus dorsi muscle
Serratus posterior superior muscle
  • Elevates the superior ribs during forced inspiration
Serratus posterior inferior muscle
  • Draws rib posteriorly and inferiorly

SALT: the Serratus Anterior muscle is innervated by the Long Thoracic nerve.

  1. Sternal Angle. https://medical-dictionary.thefreedictionary.com/sternal+angle. Updated: January 1, 2018. Accessed: December 7, 2018.
  2. The Anterolateral Abdominal Wall. http://teachmeanatomy.info/abdomen/muscles/the-abdominal-wall/. Updated: December 22, 2017. Accessed: April 19, 2018.
  3. Costovertebral joint. https://radiopaedia.org/articles/costovertebral-joint. Updated: January 1, 2018. Accessed: April 19, 2018.