Intercostal spaces
The intercostal spaces are the space between the ribs. There are 11 spaces on each side and they are numbered according to the rib which is the superior border of the space.
On this page:
Gross anatomy
The intercostal spaces contain three layers of muscle: the external, internal and innermost layers with the neurovascular bundle found between the internal and innermost layers.
Muscle layers
The external intercostal muscle is the outermost muscle of the intercostal space. This muscle has fibers which run in a downwards, forwards and medial direction from the inferior border of the superior rib to insert on the outer lip of the inferior rib.
The internal intercostal muscle is the middle layer of the intercostal space. This muscle has fibers which run in a downwards, backwards and lateral direction from the inferior border of the superior rib to insert on the superior border of the inferior rib.
The deepest layer of muscle in the intercostal space is made up of three muscles which are collectively known as the tranversus thoracis group. This group includes the subcostal muscles posteriorly, the innermost intercostals laterally, and the transversus thoracis / sternocostalis muscles anteriorly.
Neurovascular bundle
The neuromuscular bundles are found between the middle and innermost layers, protected by the costal groove of the superior rib of each intercostal space. They are ordered vein, artery, nerve from superior to inferior (mnemonic VAN). The collateral neurovascular bundle runs at the lower edge of the space, just above the inferior rib and the order is reversed, i.e. nerve, artery, vein from superior to inferior.
Blood supply
Arterial supply
The structures in each intercostal space are supplied by a single large posterior intercostal artery and 2 smaller anterior intercostal arteries.
In the first and second intercostal spaces a large posterior artery arises from the superior intercostal artery (a branch from the costocervical artery). The superior thoracic artery (from the axillary artery) often contributes also.
The arteries in the remaining spaces branch directly from the descending thoracic aorta.
The two smaller anterior arteries in the first 6 spaces arise from the internal thoracic artery and in the remaining spaces from the musculophrenic artery.
Venous drainage
Posterior veins drain into the azygos or hemiazygos veins. Anterior veins drain into the internal thoracic or musculophrenic veins.
Innervation
Each intercostal space is supplied segmentally by muscular branches of anterior rami of spinal nerves T1-T11. The branches of anterior rami of spinal nerves are:
- rami communicantes
- lateral cutaneous branch
- muscular branches
- parietal pleura branches
- parietal peritoneal sensory branches (from T7-T11 only)
- collateral branch
- terminal anterior cutaneous branch
Related pathology
The intercostal space is traversed during procedures such as pleural taps, and knowledge of the neurovascular bundle location is important to reduce the risk of hemorrhage.
A safe technique for insertion of intercostal catheters describes anatomical landmarks involving the axilla and a 'triangle of safety'.
Related Radiopaedia articles
Anatomy: Thoracic
- thoracic skeleton
- thoracic cage
- thoracic spine
- articulations
- muscles of the thorax
- diaphragm
- intercostal space
- intercostal muscles
- variant anatomy
- spaces of the thorax
- thoracic viscera
- tracheobronchial tree
-
lungs
-
bronchopulmonary segmental anatomy (Boyden Classification) (mnemonic)
- left lung
- right lung
- variant anatomy
- lung parenchyma
- hilum
- pleura
-
bronchopulmonary segmental anatomy (Boyden Classification) (mnemonic)
-
heart
- cardiac chambers
- heart valves
- pectinate muscles
- cardiac fibrous skeleton
- coronary arteries
- innervation of the heart
- fetal circulation
-
pericardium
- pericardial space
- oblique pericardial sinus
- transverse pericardial sinus
-
pericardial recesses
- aortic recesses
- pulmonic recesses
- postcaval recess
- pulmonary venous recesses
- pericardial ligaments
- epicardial fat pad
- esophagus
- thymus
- breast
- blood supply of the thorax
- arteries
-
thoracic aorta (development)
- ascending aorta
- aortic arch
- aortic isthmus
- descending aorta
- pulmonary trunk
-
thoracic aorta (development)
- veins
- superior vena cava (cavoatrial junction)
- inferior vena cava
-
coronary veins
- cardiac veins which drain into the coronary sinus
- great cardiac vein
- middle cardiac vein
- small cardiac vein
- posterior vein of the left ventricle
- vein of Marshall (oblique vein of the left atrium)
- anterior cardiac veins
- venae cordis minimae (smallest cardiac veins or thebesian veins)
- cardiac veins which drain into the coronary sinus
- pulmonary veins
- arteries
- lymphatics
- innervation of the thorax
Unable to process the form. Check for errors and try again.