Description<\/h3>\n<\/span>\n\n\n- The main branches run right under the costal groove (except for first two)<\/li>
- The collateral branches run at the bottom of the intercostal space<\/li><\/ul>\n\n\n\n
The main branches are arranged in a pattern of VAN<\/strong> \u2014 v<\/strong>ein, a<\/strong>rtery, n<\/strong>erve from top to bottom, while the collateral branches are arranged in NAV from top to bottom.<\/p>\n\n\n\n![\"\"](\"https:\/\/meddists.com\/wp-content\/uploads\/2018\/07\/intercostal-558x600.png\")
<\/a>Figure 1. <\/strong>A slice of the rib cage showing the intercostal muscles and neurovasculature<\/figcaption><\/figure>\n\n\n<\/span>\nInnervation<\/h3>\n<\/span>\n\n\nThere are 12 pairs of spinal nerves<\/strong> in the thoracic region. All of them leave from the vertebral column through the intervertebral foramina. As soon as they exit, they split into an anterior <\/strong>or ventral<\/strong> ramus<\/strong> and a posterior <\/strong>or dorsal ramus <\/strong>(see Figure 3).<\/p>\n\n\n\n![\"\"](\"https:\/\/meddists.com\/wp-content\/uploads\/2019\/03\/spinal_nerves_v1_1-600x400.png\")
<\/a>Figure 2. Cross-section of the vertebral column and spinal cord<\/strong> (Credit: DO11.10, GFD License)<\/figcaption><\/figure>\n\n\n\n- The anterior rami of the nerves T1-T11<\/strong> give the intercostal nerves<\/li>
- Most of the posterior rami<\/strong> innervate the joints, skin, deep tissues of the back of the thoracic region<\/li>
- The anterior ramus of the nerve T12<\/strong> gives the subcostal nerve<\/strong> below the 12th rib.<\/li><\/ul>\n\n\n<\/span>\n
Intercostal nerves<\/h4>\n<\/span>\n\n\nThe intercostal nerves are related to the somatic nervous system and innervate the thoracic wall. They have branches to the brachial plexus, the abdomen, and the peritoneum. The intercostal nerves can be divided into typical<\/strong> or atypical<\/strong>.<\/p>\n\n\n\n- Typical nerves (T3-T6)<\/strong>
- Runs within the endothoracic fascia<\/li>
- At the angles of the ribs, the nerves cross between the internal intercostal<\/strong> and the innermost intercostal muscles<\/strong><\/li>
- Afterward, they run beneath the costal groove.<\/li>
- These nerves give off collateral cutaneous branches<\/strong> and the anterior collateral cutaneous<\/strong> branch near the sternum.<\/li><\/ul><\/li>
- Atypical<\/strong> nerves (T1, T2, T7-T11)<\/strong>
- The T1 and T2 thoracic spinal nerves run inside the costal margins (instead of beneath the costal groove)<\/li>
- T7- T11 continues as thoracoabdominal nerves<\/strong>, providing innervation to the abdominal region as well.<\/li><\/ul><\/li>
- Subcostal nerves<\/strong>
- Consists of the anterior rami of T12 thoracic spinal nerve.<\/li>
- Branches<\/strong>
- Rami communications<\/li>
- Collateral branches<\/li>
- Lateral cutaneous<\/li>
- Anterior cutaneous<\/li>
- Muscular branches<\/li><\/ol><\/li><\/ul><\/li><\/ul>\n\n\n\n
![\"\"](\"https:\/\/meddists.com\/wp-content\/uploads\/2018\/07\/innervation-thorax-600x600.png\")
<\/a>Figure 3. Intercostal nerves and their branches<\/strong><\/figcaption><\/figure>\n\n\n<\/span>\nBlood supply<\/h3>\n<\/span>\n\n\nThe blood supply of the thoracic wall comes from three main sources:<\/p>\n\n\n\n
- Thoracic aorta<\/strong>
- Posterior intercostal arteries<\/li>
- Subcostal arteries<\/li><\/ul><\/li>
- Subclavian artery<\/strong>
- Thyrocervical trunk \u2014 Internal thoracic artery<\/li>
- Costocervical trunk \u2014 Supreme (superior) intercostal artery<\/li><\/ul><\/li>
- Axillary artery<\/strong>
- Lateral thoracic arteries<\/li>
- Superior Thoracic arteries<\/li><\/ul><\/li><\/ol>\n\n\n<\/span>\n
Intercostal arteries<\/h4>\n<\/span>\n\n\n- Except for the 10th and 11th intercostal space, all of the intercostal arteries pass between the ribs<\/li>
- Each intercostal space is supplied by three arteries:
- A single posterior intercostal artery<\/strong> which is the larger one (and its collateral branch)<\/li>
- A pair of anterior intercostal arteries <\/strong>which are smaller<\/li><\/ul><\/li><\/ul>\n\n\n<\/span>\n
Posterior intercostal arteries<\/h4>\n<\/span>\n\n\n- The supreme (superior) intercostal artery<\/strong> provide the 1st and 2nd intercostal posterior intercostal arteries<\/li>
- The thoracic aorta<\/strong> provide the remaining posterior intercostal arteries<\/li>
- All of the posterior intercostal arteries pass between the internal and innermost intercostal muscles and supply the overlying skin, the muscles, and the parietal pleura surrounding the lungs<\/li><\/ul>\n\n\n<\/span>\n
Anterior intercostal artery<\/h4>\n<\/span>\n\n\n- The internal thoracic branch supplies the 1st-6th intercostal spaces<\/li>
- The musculophrenic branch supplies the 7th-9th intercostal spaces<\/li>
- Supplies the same regions as the Posterior intercostal arteries<\/li><\/ul>\n\n\n<\/span>\n
Internal thoracic artery<\/h4>\n<\/span>\n\n\n- A branch of the subclavian artery<\/li>
- Gives rise to the superior epigastric<\/strong> and the and musculophrenic arteries<\/strong><\/li>
- Supplies the anterior intercostal arteries of the 1st\u20136th intercostal spaces<\/li><\/ul>\n\n\n<\/span>\n
Subcostal artery<\/h4>\n<\/span>\n\n\n- Branches off the thoracic aorta<\/strong><\/li>
- Found at the inferior border of the 12th rib<\/li>
- Supplies the anterolateral abdominal wall<\/strong><\/li><\/ul>\n\n\n<\/span>\n
Venous drainage<\/h3>\n<\/span>\n\n\n- Brachiocephalic veins<\/strong> \u2014 Usually drain the 1st intercostal space<\/li>
- Superior intercostal vein <\/strong>\u2014 Usually forms from the drainage of the 2-4th intercostal spaces<\/li>
- Azygos vein <\/strong>\u2014 Drains the posterior 5-11th intercostal spaces (right side)<\/li>
- Accessory-hemiazygos vein<\/strong> \u2014 Drains the posterior 5-8th intercostal space (left side)<\/li>
- Hemiazygos vein<\/strong> \u2014 Drains the posterior 9-11th intercostal spaces (left side)<\/li>
- Internal thoracic vein<\/strong><\/li>
- Subcostal vein<\/strong><\/li>
- Intercostal veins<\/strong> \u2014 Run along the intercostal arteries and nerves and lie most superior within the costal grooves. The 11 posterior and anterior intercostal veins anastomose freely.<\/li><\/ol>\n\n\n<\/span>\n
Azygos-hemiazygos system<\/h4>\n<\/span>\n\n\nThe azygos-hemiazygos system is discussed in depth in its\u00a0own article<\/a>.<\/em><\/p>\n\n\n\nThe majority of the intercostal veins drain into the azygos\/hemiazygos veins.<\/p>\n\n\n\n
- The accessory-hemiazygos and hemiazygos veins drain to the azygos vein roughly at T7-T8<\/li>
- The azygos vein empties to the superior vena cava at T4<\/li><\/ul>\n\n\n\n
![\"\"](\"https:\/\/meddists.com\/wp-content\/uploads\/2018\/07\/thoracic-venous-drainage-600x234.png\")
<\/a>Figure 4. Thoracic venous drainage<\/strong> (Credit: OpenStax, CC BY-SA 4.0<\/a>)<\/figcaption><\/figure>\n\n\n<\/span>\nClinical information<\/h3>\n<\/span>\n\n\nCertain conditions such as fluids in the pleural cavity may require drainage. This can be done through a needle or a chest tube<\/strong> (see Figure 5).<\/p>\n\n\n\nThe needlee is inserted through a puncture made at the lower part of the intercostal space<\/strong> in order to prevent any damage to the major neurovasculature. The collateral may be damaged, but they are far less important.<\/p>\n\n\n\n![\"\"](\"https:\/\/meddists.com\/wp-content\/uploads\/2018\/07\/chest-tube-600x450.png\")
<\/a>Figure 5. Chest tube<\/strong> (Credit: C. H. Chen, S. Y. Lee et al.)<\/figcaption><\/figure>\n<\/span>
The main branches are arranged in a pattern of VAN<\/strong> \u2014 v<\/strong>ein, a<\/strong>rtery, n<\/strong>erve from top to bottom, while the collateral branches are arranged in NAV from top to bottom.<\/p>\n\n\n\n There are 12 pairs of spinal nerves<\/strong> in the thoracic region. All of them leave from the vertebral column through the intervertebral foramina. As soon as they exit, they split into an anterior <\/strong>or ventral<\/strong> ramus<\/strong> and a posterior <\/strong>or dorsal ramus <\/strong>(see Figure 3).<\/p>\n\n\n\n The intercostal nerves are related to the somatic nervous system and innervate the thoracic wall. They have branches to the brachial plexus, the abdomen, and the peritoneum. The intercostal nerves can be divided into typical<\/strong> or atypical<\/strong>.<\/p>\n\n\n\n The blood supply of the thoracic wall comes from three main sources:<\/p>\n\n\n\n The azygos-hemiazygos system is discussed in depth in its\u00a0own article<\/a>.<\/em><\/p>\n\n\n\n The majority of the intercostal veins drain into the azygos\/hemiazygos veins.<\/p>\n\n\n\n Certain conditions such as fluids in the pleural cavity may require drainage. This can be done through a needle or a chest tube<\/strong> (see Figure 5).<\/p>\n\n\n\n The needlee is inserted through a puncture made at the lower part of the intercostal space<\/strong> in order to prevent any damage to the major neurovasculature. The collateral may be damaged, but they are far less important.<\/p>\n\n\n\n![\"\"](\"https:\/\/meddists.com\/wp-content\/uploads\/2018\/07\/intercostal.png\")
<\/a>Innervation<\/h3>\n<\/span>\n\n\n
<\/a>Intercostal nerves<\/h4>\n<\/span>\n\n\n
<\/a>Blood supply<\/h3>\n<\/span>\n\n\n
Intercostal arteries<\/h4>\n<\/span>\n\n\n
Posterior intercostal arteries<\/h4>\n<\/span>\n\n\n
Anterior intercostal artery<\/h4>\n<\/span>\n\n\n
Internal thoracic artery<\/h4>\n<\/span>\n\n\n
Subcostal artery<\/h4>\n<\/span>\n\n\n
Venous drainage<\/h3>\n<\/span>\n\n\n
Azygos-hemiazygos system<\/h4>\n<\/span>\n\n\n
<\/a>Clinical information<\/h3>\n<\/span>\n\n\n
<\/a>