AN23.1-6 | Mediastinum — Glossary

The central compartment of the thorax between the pleural cavities, divided into superior and inferior (anterior, middle, posterior)

The part of the mediastinum above the sternal angle plane (T4/T5), containing the arch of aorta, SVC, trachea, oesophagus, and thymus

The part behind the pericardium and above the diaphragm, containing the descending aorta, oesophagus, azygos system, and thoracic duct

The main lymphatic channel draining the entire body below the diaphragm plus the left head, neck, and thorax, emptying into the left venous angle

A sac-like dilatation at L1-L2 where the thoracic duct begins, collecting lymph from the abdomen and lower limbs

A venous channel on the right side draining the posterior thoracic wall, arching over the right lung root to enter the SVC

A venous channel on the left lower thorax that crosses the midline at T8-T9 to join the azygos vein

Four points where the oesophagus is narrowed: cricoid (15cm), aortic arch (22.5cm), left bronchus (27.5cm), diaphragmatic hiatus (40cm)

Cranial nerve X providing parasympathetic innervation to thoracic and abdominal viscera, with recurrent laryngeal branches to the larynx

A branch of the vagus that loops under the aortic arch (left) or subclavian artery (right) to ascend and supply laryngeal muscles

The sole motor nerve to the diaphragm (C3, C4, C5), running on the lateral aspect of the pericardium

A chain of ganglia lateral to the vertebral column providing sympathetic innervation to thoracic and abdominal viscera

Pre-ganglionic sympathetic fibres from T5-T9 passing to the coeliac ganglion for abdominal visceral innervation

Miosis, ptosis, and anhidrosis from sympathetic chain disruption, seen after thoracic surgery or apical lung tumour

The internal ridge at the tracheal bifurcation; widening beyond 70 degrees on CXR suggests subcarinal lymphadenopathy

Obstruction of the superior vena cava by mediastinal mass (lymphoma, thymoma) causing facial swelling, distended neck veins, and dyspnoea

A lymphoid organ in the anterior superior mediastinum, large in children, involuting to fat in adults; site of T-cell maturation

Right (short, vertical) and left (long, horizontal) veins joining behind the right first costal cartilage to form the SVC

The curved portion of the aorta at T4 giving three branches: brachiocephalic trunk, left common carotid, and left subclavian arteries

The opening in the diaphragm at T10 through which the oesophagus and vagal trunks pass, 2 cm left of midline

The opening in the diaphragm at T12 posterior to the median arcuate ligament, transmitting the aorta, azygos vein, and thoracic duct