Anaes · Applied anatomy

Thorax, mediastinum and heart anatomy

Also known as Thoracic anatomy · Mediastinum · Heart anatomy · Coronary arteries · Great vessels · Intercostal block

The thorax houses the heart and great vessels, the lungs and the central airway, and is the setting for central venous cannulation, intercostal and paravertebral block, pericardiocentesis and cardiac surgery. The framework rests on six exam-critical ideas. First, the thoracic cage is built of 12 thoracic vertebrae, 12 pairs of ribs and the sternum (manubrium, body and xiphoid); the intercostal space carries the nerve-artery-vein triad in the costal groove in the order V-A-N (vein superior, artery, nerve inferior) running along the lower border of the rib above — the basis for intercostal block and for the rule to needle just above the upper border of the rib below. Second, the mediastinum is the central compartment between the pleural cavities; it is divided into the SUPERIOR mediastinum (above the sternal angle) and the INFERIOR mediastinum, the latter split into ANTERIOR (thymus, behind the sternum), MIDDLE (the heart and pericardium) and POSTERIOR (oesophagus, thoracic aorta, thoracic duct, azygos, vagus). Third, the heart has four chambers (right and left atria, right and left ventricles), an apex (left fifth intercostal space, midclavicular line), three surfaces (anterior/sternocostal, inferior/diaphragmatic, posterior/base) and borders (right atrial, left ventricular), and sits in the middle mediastinum within the pericardium. Fourth, the coronary arteries are the right coronary artery (RCA, supplying the inferior wall and often the AV node), the left anterior descending (LAD, the anterior wall and interventricular septum — the 'widow-maker' territory) and the circumflex (the lateral wall); coronary dominance is determined by which artery supplies the posterior descending artery (usually the RCA — right dominant). Fifth, the cardiac conduction system runs from the SA node (high right atrium, the pacemaker) through the atria to the AV node (lower right atrium, near the coronary sinus), then to the bundle of His, its branches and the Purkinje fibres; angiographic data show the AV node arises from the RCA in about 72% but the SA node from the RCA in only about 53% — so nodal supply is less right-sided than classic teaching suggests. Sixth, the thoracic duct ascends from the cisterna chyli through the aortic hiatus, crosses from right to left at the T4-T5 level, and empties into the left venous angle — the reason a right internal-jugular line rarely causes chylothorax but can injure the duct, and a left one can. Built on the sternal-healing study (Sarrazin 2026), the mediastinal-imaging study (Dogan 2026), the chylothorax-after-IJV-cannulation report (Alsadeh 2026), the coronary-anastomosis imaging study (Soto Diaz 2026), the sinus-of-Valsalva study (Majadla 2026), the ultrasound intercostal-block study (Yang 2026), the intercostal-cryoanalgesia study (Drake 2026), the sinoatrial-node report (Tang 2026), the nodal-artery-origin angiographic study (Ramanathan 2009), and the foreign-body-aspiration bronchial-anatomy study (Yildiran 2026).