Vasculature of the Thoracic Wall

Arterial Supply

The thoracic wall receives a rich arterial supply via branches of the subclavian artery, axillary artery and thoracic aorta:

Anterior Intercostal Arteries

The anterior intercostal arteries supply the 1st to 9th intercostal spaces, with two arteries present in each space. Their origin varies according to level:

• 1st–6th intercostal spaces – internal thoracic artery
• 7th–9th intercostal spaces – musculophrenic artery

Within each space, the anterior intercostal arteries divide into a superior branch, which travels in the costal groove of the upper rib, and an inferior collateral branch, which runs along the upper border of the rib below.

They anastomose with the posterior intercostal arteries at the costochondral junction.

By TeachMeSeries Ltd (2026)

Fig 1
The origin and course of the anterior and posterior intercostal arteries.

Posterior Intercostal Arteries

There is one posterior intercostal artery in each intercostal space. The source of these vessels differs by intercostal level:

• 1st and 2nd intercostal spaces – superior intercostal artery (branch of the subclavian artery)
• 3rd–11th intercostal spaces – posterior aspect of the thoracic aorta

After arising, each posterior intercostal artery gives off a branch to supply the spinal cord, vertebral column and back musculature.

They then pass laterally within the costal groove of each rib, accompanied by the intercostal vein and nerve. In this location, they lie between the internal and innermost intercostal muscles.

Each artery gives off a collateral branch, which descends to run along the superior border of the rib below and anastomoses with the corresponding collateral anterior intercostal artery.

The main vessel continues anteriorly within the costal groove, ultimately anastomosing with the anterior intercostal artery proper at the costochondral junction.

Supplementary Arterial Supply

Further arterial supply to the thoracic wall is provided by the internal thoracic artery and branches of the axillary artery.

The internal thoracic artery contributes via perforating branches, which pass through the intercostal spaces to supply the overlying pectoral muscles and skin. It also provides additional supply via its terminal branches:

• Musculophrenic artery – supplies the lower intercostal spaces and diaphragm.
• Superior epigastric artery – contributes to the anterior abdominal wall.

Additional contributions from the axillary artery are via the superior thoracic and lateral thoracic arteries, which supply the upper and lateral aspects of the thoracic wall.

By TeachMeSeries Ltd (2026)

Fig 2
Anatomical course of the internal mammary artery.

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Venous Drainage

The venous drainage of the thoracic wall broadly mirrors the arterial supply, with veins accompanying the corresponding arteries within each intercostal space.

Each intercostal space is drained by the following vessels:

• Anterior intercostal veins (11 pairs) – drain into the internal thoracic vein and musculophrenic vein.
• Posterior intercostal veins (11 pairs) – drain into the azygos system (pattern varies by level, see below).
• Subcostal veins (1 pair) – run inferior to the 12th rib and drain into the azygos system.

The drainage pattern of the posterior intercostal veins is variable, but a common arrangement is:

Intercostal Neurovascular Bundle

The intercostal neurovascular bundle is a key anatomical structure of the thoracic wall, consisting of the intercostal vein, artery and nerve.

It runs within the costal groove along the inferior border of each rib, lying between the internal and innermost intercostal muscles. The structures are arranged from superior to inferior as vein, artery, nerve (VAN).

This arrangement is clinically important, as procedures involving the thoracic wall must avoid the main bundle to prevent injury.

By TeachMeSeries Ltd (2026)

Fig 3
The intercostal bundle within the costal groove.

Clinical Relevance

Chest Drain Insertion

Chest drains are inserted into the pleural cavity to remove air, fluid or blood, typically within the “safe triangle” of the lateral chest wall. The boundaries of the safe triangle are:

• Anterior – lateral border of pectoralis major
• Posterior – anterior border of latissimus dorsi
• Inferior – a horizontal line superior to the 5th intercostal space

Placement within this region helps avoid injury to deeper structures such as the diaphragm, abdominal organs and major neurovascular structures.

The position of the intercostal neurovascular bundle is a key anatomical consideration. This bundle runs within the costal groove along the inferior border of each rib, containing the intercostal vein, artery and nerve.

To reduce the risk of injury to the main intercostal neurovascular bundle, the drain should be inserted just superior to the upper border of a rib. Incorrect placement along the inferior border may result in vascular injury or damage to the intercostal nerve, leading to bleeding or neuropathic pain.

By Rebecca Varley, TeachMeSurgery [CC-BY-NC-ND 4.0]

Fig 4
The triangle of safety for chest drain insertion