--- module: 077-01 language: en chapter: 77 title: "Thoracic Anatomy, Mediastinum, Heart, Lungs, and Chest Wall" module_title: "Thoracic wall, diaphragm, pleura, and surface anatomy" source_sha256: ddcf1753067a59abc43f279f2d8addca73b798399cce399d9585cd2eab5cb0d1 --- # Thoracic wall, diaphragm, and pleura ## Deformable protective cage ### Changes volume with every breath ### Wall, diaphragm, pleura as one mechanical system ### Landmarks shift with respiration, posture, age, disease ## Boundaries and apertures ### Vertebrae, ribs, cartilages, sternum, joints ### Superior aperture: T1, first ribs, manubrium #### Slopes down anteriorly #### Transmits trachea, oesophagus, vessels, nerves ### Crowded root of neck #### Artery and plexus pass between scalenes #### Vein anterior to anterior scalene #### Cervical rib or band can compress #### Narrowing alone is not outlet syndrome ### Inferior aperture closed by diaphragm ### Sternal angle at second costal cartilage #### Permits rib counting #### T4-T5 disc and mediastinal plane ## Ribs and articulations ### Head, neck, tubercle, angle, shaft, groove ### Head meets own and upper vertebra ### True ribs attach directly to sternum ### False ribs join cartilage above #### Form the costal margin ### Floating ribs lack anterior attachment ### Rib one grooved by subclavian vessels ### Movement patterns #### Pump handle raises anteroposterior diameter #### Bucket handle raises transverse diameter ## Intercostal spaces ### External, internal, innermost layers #### External inferoanterior, membrane anteriorly #### Internal inferoposterior, membrane posteriorly ### Bundle in costal groove: vein, artery, nerve #### Collaterals near upper border of rib below #### Procedures aim just above a rib ### Posterior arteries mostly from aorta ### Anterior arteries from internal thoracic ### Intercostal nerves T1 to T11, T12 subcostal #### Supply muscle, skin, parietal pleura #### T2 intercostobrachial explains referred pain ## Diaphragm as muscle and partition ### Sternal, costal, lumbar origins to central tendon ### Right dome higher because of liver ### Contraction lowers domes, raises abdominal pressure ### Breathing mechanics #### Quiet inspiration: more negative pleural pressure #### Forced inspiration: scalenes, sternocleidomastoid #### Quiet expiration is elastic recoil #### Forced expiration pushes diaphragm up ### Openings #### Caval opening T8 in central tendon #### Oesophageal hiatus T10 in right crus #### Aortic hiatus T12 with thoracic duct ### Phrenic C3 to C5 motor and central sensation #### Central irritation refers to shoulder #### Periphery via lower intercostal nerves ### Paralysis: paradoxical rise, less ventilation ## Pleura and recesses ### Visceral pleura reflects to parietal ### Potential space with lubricating film #### Negative pressure couples lung to wall ### Cervical pleura rises above first rib #### Neck injury or subclavian procedures enter ### Lung border ribs six, eight, ten #### Pleura about two ribs lower ### Costodiaphragmatic recess collects fluid ### Pain sensitivity #### Visceral pleura relatively insensitive #### Parietal pleura painful via intercostal, phrenic ## Breast and anterior wall ### Suspensory ligaments, retromammary plane ### Internal thoracic and lateral thoracic supply ### Lymph mainly to axillary nodes #### Oedema, retraction, fixation nonspecific alone ### Axillary nerves at surgical risk #### Long thoracic on serratus anterior #### Intercostobrachial numbness and pain ## Procedures and trauma ### Drains need pleural and organ limits ### Safe triangle for tube thoracostomy ### Rib fractures impair ventilation #### Upper ribs signal high energy #### Lower ribs: liver, spleen, kidney #### Flail failure reflects contusion and pain ### Pneumothorax separates pleural layers #### Tension impairs venous return, decompress now ### Blood, chyle, pus, effusion share the space ### Landmarks are a map, not certainty