Chest wall

Summary

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.

Overview

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

Reference lines
Anterior chest
Posterior chest
Axilla

  • Vasculature and innervation: neurovascular bundles
    • Each bundle is composed of an intercostal vein (most superior), intercostal artery , and intercostal nerve (most inferior).
    • They course along the costal groove at the inferior border of each rib.

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.

Rib cage

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

Ribs

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

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][2]

Musculature

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

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

Other muscles that attach to the thoracic wall include:

Muscles Origin Insertion Innervation Function
Pectoralis major Medial clavicle, anterior sternum, and six upper costal cartilages Proximal humerus
  • Flexes, adducts and medially rotates the arm
  • Accessory muscle of respiration
Pectoralis minor Ribs 3–5 near costal cartilages Medial border of the scapula's coracoid process Medial pectoral nerve
  • Stabilization of the scapula
  • Accessory muscle of respiration
Serratus anterior Upper borders of ribs 1–8 Medial scapula Long thoracic nerve
  • Rotation of the scapula
  • Accessory muscle of respiration
Subclavius Rib 1 near costal cartilage Deep surface of clavicle Subclavian nerve
Latissimus dorsi Posterior ilium, sacrum, spinous processes of T6–L5, thoracolumbar fascia (the deep fascia of the trunk) , posterior ribs 8–12, and inferior angle of scapula Intertubercular groove of the humerus Thoracodorsal nerve
Serratus posterior superior Spinous processes of C7–T3 Ribs 2–5 Intercostal nerves
  • Elevates the superior ribs during forced inspiration
Serratus posterior inferior Spinous processes of T11–L2 Ribs 9–12 Intercostal nerves
  • Draws rib posteriorly and inferiorly

Embryology

References:[3]

Clinical significance