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 .
- Protection of thoracic organs
- Stabilization of
- Dynamic expansion and recoil during respiration ( )
- Reference lines
- Surface anatomy: See “ .”
- Vasculature and innervation: neurovascular bundles
Below each rib parks a VAN: Vein, Artery, Nerve (intercostal bundles from superior to inferior).
- Composed of 3 flat bones
- Suprasternal notch: visible and palpable U-shaped depression above the manubrium between the two clavicles
- Sternal angle
There are 12 pairs of ribs separated by intercostal spaces (ICSs)
- Parts of a typical rib
- 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).
- Costovertebral joints: Connect the rib heads to the vertebral bodies.
- Costotransverse joints: Connect the rib tubercle to the transverse processes of the vertebral bodies.
Intercostal surface projections
- Nipples in men: ∼ 5th ICS, can be lower in women
- Dome of the diaphragm and liver: right 5th ICS at the midclavicular line
- Lung: see
- Right margin: extends from right 3rd costal cartilage to right 6th costal cartilage
- Left margin: extends from left 2nd ICS to the apex at the midclavicular line of the 5th ICS
- Anterior interventricular sulcus: 2.5 cm lateral of the midline at 3rd left ICS
- For the projection of the heart valves and the auscultation of the heart sounds, see .
The chest wall is comprised of 5 muscles, which are all innervated by the intercostal nerves:
|Overview of chest wall muscles|
|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|
|Pectoralis major muscle|| |
|Pectoralis minor muscle|| || |
|Serratus anterior muscle|| |
|Subclavius muscle|| |
|Latissimus dorsi muscle|
|Serratus posterior superior muscle|| || || |
|Serratus posterior inferior muscle|| || || |
SALT: the Serratus Anterior muscle is innervated by the Long Thoracic nerve.
- Trunk develops from paraxial and lateral plate mesoderm
- Failure of the fusion of the sternal bars results in a cleft sternum
- A rare congenital condition in which the heart is completely or partially located outside the thoracic cavity
- Impaired migration of lateral mesoderm to the midline results in incomplete fusion of the anterior chest wall
- Associated with omphalocele, congenital diaphragmatic hernia, sternal cleft, and congenital heart defects
- Xiphoid process does not ossify until after birth, unlike the rest of the sternum
- Excessive depression and rotation of the sternum: