The Heart: A Vital Organ – Understanding Its Role

The heart is a vital muscular organ located in the mediastinum, slightly left of midline, protected by the rib cage. It functions as a dual pump maintaining systemic and pulmonary circulation.

Anatomy & Flow

1. Right Atrium: Receives deoxygenated blood from SVC, IVC, coronary sinus.
2. Right Ventricle: Pumps blood → pulmonary artery → lungs (oxygenation).
3. Left Atrium: Receives oxygenated blood from pulmonary veins.
4. Left Ventricle: Pumps blood → aorta → systemic circulation.

Key Features

• Four Valves: Tricuspid, pulmonary, mitral, aortic — ensure unidirectional flow.
• Coronary Circulation: Supplies the heart itself (RCA, LAD, LCx).
• Conduction System: SA node (pacemaker) → AV node → Bundle of His → Purkinje fibers.
• Pericardium: Fibrous sac with serous lining (lubrication, restraint).

Physiology

• Cardiac Output: HR × Stroke Volume (~5 L/min at rest).
• Regulation: Autonomic (sympathetic ↑HR/contractility; parasympathetic ↓HR), hormonal (catecholamines, ANP, RAAS), intrinsic (Frank-Starling).
• Electrical-Mechanical Coupling: AP → Ca²⁺-induced Ca²⁺ release → contraction.

Clinical Importance

Cardiovascular disease (ischemic, hypertensive, valvular, arrhythmic, heart failure) is the leading global cause of death. Prevention: control BP, lipids, diabetes, weight; exercise; no smoking; healthy diet.