AN24.1-6 | Lungs & Trachea — Glossary

A fibrocartilagenous tube of 16-20 C-shaped cartilage rings from C6 to T4/T5 carina, bifurcating into right and left main bronchi

The internal cartilaginous ridge at the tracheal bifurcation; widening on CXR suggests subcarinal pathology

Wider (2.5cm), shorter (2.5cm), and more vertical (25 degrees) than the left, making it the preferred pathway for aspirated foreign bodies

A wedge-shaped, functionally independent unit of lung with its own segmental bronchus and pulmonary artery branch

A tongue-shaped projection of the left upper lobe that is the functional equivalent of the right middle lobe

The right upper lobe bronchus, so named because it arises above the right pulmonary artery

Low-pressure, high-volume circulation carrying deoxygenated blood from the right ventricle to alveolar capillaries for gas exchange

Branches from the descending aorta providing oxygenated nutritive blood supply to lung tissue, bronchial walls, and visceral pleura

The serous membrane covering the lung surface and dipping into fissures, supplied by bronchial arteries, with no pain fibres

The serous membrane lining the thoracic wall, diaphragm, and mediastinum, with pain fibres from intercostal and phrenic nerves

The largest pleural recess where costal and diaphragmatic parietal pleura meet, the site for thoracocentesis and chest drain insertion

A pleural recess behind the sternum where costal and mediastinal parietal pleura meet

The area on the medial surface where the bronchus, pulmonary vessels, lymphatics, and nerves enter and leave the lung

An indentation on the anterior border of the left lung created by the heart, exposing the pericardium

Approximately 300 million tiny air sacs providing 70 square metres of surface area for gas exchange

Air in the pleural cavity causing lung collapse; tension pneumothorax is a life-threatening emergency requiring immediate decompression

Fluid accumulation in the pleural cavity, detected by percussion dullness and absent breath sounds

Ventilation-perfusion ratio, highest at the lung apex explaining why TB favours the apical segments

Surgical removal of a single bronchopulmonary segment, possible because pulmonary veins run between segments

Surgical opening in the trachea between rings 2-4, below the cricoid cartilage, avoiding the thyroid isthmus

A fissure present in both lungs separating the lower lobe from the upper (and middle on the right)

A fissure unique to the right lung separating the upper lobe from the middle lobe