AN25.1-9 | Thorax — Glossary

A half-moon shaped articular surface on the superior or inferior margin of a thoracic vertebral body that, together with the demifacet of an adjacent vertebra, forms a complete facet for rib head articulation.

Ribs 1-7 that attach directly to the sternum via their own individual costal cartilages; also called vertebrosternal ribs.

Ribs 8-10 whose costal cartilages do not attach directly to the sternum but join the costal cartilage of the rib above; also called vertebrochondral ribs.

Ribs 11 and 12 that have no anterior attachment to the sternum or costal cartilage of other ribs; their anterior ends are free.

A shallow groove on the inner surface of the inferior border of a rib that shelters the intercostal neurovascular bundle (vein, artery, nerve).

The group of structures running along the costal groove in the order Vein-Artery-Nerve (VAN) from superior to inferior, supplying each intercostal space.

The most superficial of the three intercostal muscle layers, with fibres directed inferomedially (hands-in-pockets direction); active in inspiration.

The middle intercostal muscle layer with fibres directed superolaterally (perpendicular to externals); the interosseous part aids forced expiration.

The deepest intercostal muscle layer, separated from the internal intercostal by the neurovascular bundle; incomplete and variable.

The primary muscle of respiration; a dome-shaped musculotendinous partition separating the thoracic and abdominal cavities, with sternal, costal, and vertebral origins inserting into a central tendon.

The trefoil-shaped (clover-shaped) aponeurotic centre of the diaphragm into which all muscle fibres converge; it does not attach to bone.

The larger of the two muscular pillars of the diaphragm, arising from the bodies of L1-L3 vertebrae; its fibres form part of the oesophageal hiatus.

The smaller muscular pillar of the diaphragm, arising from the bodies of L1-L2 vertebrae.

An aperture in the central tendon of the diaphragm at the T8 vertebral level transmitting the inferior vena cava and right phrenic nerve.

An opening in the muscular part of the diaphragm (right crus) at the T10 vertebral level transmitting the oesophagus and vagus nerve trunks.

A posterior opening behind the diaphragm at the T12 vertebral level transmitting the aorta, thoracic duct, and azygos vein.

The superior thoracic aperture bounded by T1 posteriorly, the first ribs laterally, and the manubrium sterni anteriorly; passage for trachea, oesophagus, and great vessels.

The inferior thoracic aperture bounded by T12, the 12th ribs, costal margins, and xiphoid process; closed by the diaphragm.

The palpable ridge at the manubriosternal joint at the T4/T5 level; landmark for the 2nd costal cartilage, tracheal bifurcation, and division of the mediastinum.

The acute angle formed by the diaphragm and chest wall on a chest X-ray; blunting indicates pleural effusion.

An anomalous extra rib arising from the C7 vertebra, present in about 0.5-1% of the population; may compress the brachial plexus or subclavian vessels causing thoracic outlet syndrome.

A clinical condition caused by compression of neurovascular structures (brachial plexus, subclavian vessels) at the thoracic outlet, often associated with a cervical rib or fibrous band.

The ratio of the maximum transverse cardiac diameter to the maximum internal thoracic diameter on a PA chest X-ray; a ratio greater than 0.5 suggests cardiomegaly.

A branch of the subclavian artery descending 1 cm lateral to the sternal border, giving off anterior intercostal arteries to supply the anterior chest wall; also used as a coronary bypass graft.

The anatomical area bounded by the anterior border of latissimus dorsi, lateral border of pectoralis major, and a horizontal line at the level of the nipple (5th ICS); the recommended site for intercostal drain insertion.