Lab: Case-based Heart Anatomy

This laboratory session integrates structural cardiac anatomy with clinical case presentations to consolidate understanding of pericardial disease, coronary anatomy, valve disease, and conduction.

The pericardium has three functional layers: fibrous pericardium (outer), parietal serous pericardium, and visceral serous pericardium (epicardium). The fibrous pericardium attaches superiorly to the adventitia of the great vessels, inferiorly to the central tendon of the diaphragm, and anteriorly to the posterior sternum via sternopericardial ligaments. The phrenic nerves (C3-C5) run lateral to the pericardium, innervating both the pericardium and diaphragm. The transverse pericardial sinus separates arteries from veins; during cardiac surgery a finger placed here allows clamping of the aorta and pulmonary trunk together.

Pericarditis causes pleuritic chest pain worsened by inspiration because diaphragmatic descent moves the inflamed pericardial layers against each other, stimulating the phrenic nerves. Cardiac tamponade results from rapid pericardial fluid accumulation — the non-distensible fibrous pericardium prevents cardiac expansion → compresses both ventricles → biventricular failure → obstructive shock.

Coronary anatomy is clinically crucial. The right coronary artery (RCA) supplies the right ventricle, parts of the posterior septum, and the SA and AV nodes — RCA occlusion causes inferior MI (II, III, aVF) and may also cause bradycardia or heart block from node ischaemia. The left coronary artery (LCA) divides into the left anterior descending (LAD, which supplies anterior LV and anterior septum) and the circumflex (Cx, which supplies the lateral LV wall). The coronary arteries are functional end-arteries — limited anastomoses mean blockage causes infarction.

When the aortic valve closes, elastic recoil of the aorta pushes blood back into the coronary ostia, filling the coronary arteries during diastole. AV valves (mitral, tricuspid) differ from semilunar valves (aortic, pulmonary) by having chordae tendineae and papillary muscle attachments that prevent prolapse. Auscultation sites reflect downstream sound propagation, not anatomical valve location. The SA node is located at the junction of the crista terminalis and the superior vena cava in the right atrial wall.