--- module: 077-03 language: en chapter: 77 title: "Thoracic Anatomy, Mediastinum, Heart, Lungs, and Chest Wall" module_title: "Lungs, airways, pulmonary vessels, lymphatics, and thoracic localisation" source_sha256: d0008f241471c2eaa92b6acea34ddbac20ef38caf8aa289a2f2b29977c233157 --- # Lungs, airways, and thoracic localisation ## Right and left lungs ### Right shorter and wider from liver ### Left has cardiac notch and lingula ### Right three lobes, left two ### Fissures variable or incomplete #### Alter collateral ventilation and spread ### Root in pleural sleeve #### Pulmonary ligament below root ### Hilar order #### Right upper bronchus above artery #### Left artery above bronchus #### Front to back: vein, artery, bronchus ## Tracheobronchial tree ### Trachea from cricoid near C6 #### C-shaped rings, membranous back wall #### Carina near sternal-angle plane ### Right main bronchus wider, shorter, vertical #### Aspiration favours right, posture decides ### Segments: bronchus plus arterial branch #### Veins run between segments #### Resectable along connective planes ### Right lung ten segments ### Bronchioles lack cartilage and glands #### Terminal bronchiole ends conducting zone ### Collateral channels bypass obstruction #### Also permit spread #### Complete fissures limit interlobar flow ### Sequestration: systemic supply, no bronchus ## Acini and alveoli ### Acinus distal to terminal bronchiole ### Secondary lobule seen on high-resolution CT ### Type one cells form gas-exchange surface ### Type two cells make surfactant, regenerate ### Macrophages clear particles and microbes ### Fused basal laminae minimise diffusion ### Surfactant lowers surface tension #### Stabilises alveoli, raises compliance #### Loss causes collapse and distress ## Dual blood supply ### Pulmonary arteries follow bronchi ### Pulmonary veins intersegmental to left atrium ### Bronchial arteries feed airways and pleura #### Return via pulmonary veins as shunt ### Low-pressure, compliant pulmonary circuit #### Emboli often in lower lobes #### Dual supply limits infarction ### Severe haemoptysis mainly bronchial #### Embolisation needs spinal artery map ## Lymphatic drainage ### Subpleural and peribronchial plexuses ### Hilar to tracheobronchial to paratracheal ### Left lower lobe can drain right #### Affects cancer staging and spread ### No lymphatics in alveolar walls ### Nodal stations defined anatomically #### Endobronchial ultrasound samples hilar nodes #### Oesophageal ultrasound reaches posterior nodes ## Autonomic and sensory supply ### Pulmonary plexuses: vagal and sympathetic ### Parasympathetic constricts, secretes ### Sympathetic dilates via catecholamines ### Vagal afferents carry stretch reflexes ### Parenchyma insensitive, parietal pleura painful ### Cough receptors in larger airways ## Localising disease ### Aspiration follows dependent segments #### Upright: basal lower lobe #### Supine: superior lower, posterior upper ### Collapse pulls structures toward lesion ### Consolidation keeps volume, air bronchograms ### Pleural disease follows surfaces and fissures #### Loculation constrained by adhesions #### Empyema lenticular, abscess in parenchyma ### Apical tumour invades plexus, sympathetics #### Hand weakness, pain, Horner syndrome ### Central tumours obstruct and invade ## Reading thoracic images ### Frontal film: systematic anatomical tour #### Hilar density mainly vascular #### Left hilum usually higher #### Rotation and low inspiration mimic disease ### Silhouette sign localises opacity #### Right border: middle lobe #### Left border: lingula ### Axial: aorta left, azygos right ### Follow findings across planes ### Branching and boundaries organise the chest