Memory tricks for the heart and vessels

Deoxygenated blood returns from the body via the superior and inferior vena cava into the Right Atrium → through the tricuspid valve → Right Ventricle → through the pulmonary valve → Pulmonary arteries → Lungs (oxygenated) → Pulmonary veins → Left Atrium → through the mitral (bicuspid) valve → Left Ventricle → through the aortic valve → Aorta → Body. Remember: Pulmonary arteries carry DEoxygenated blood — the only arteries that do.

All four heart valves prevent backflow of blood. TPMA follows blood flow from right to left. Tricuspid (right AV valve) has 3 leaflets. Pulmonary semilunar valve separates RV from pulmonary trunk. Mitral (left AV, bicuspid) has 2 leaflets — most commonly affected in rheumatic fever. Aortic semilunar valve separates LV from aorta — aortic stenosis is the most common valve disease in adults.

The SA node is the pacemaker of the heart — fires at 60-100 bpm naturally. Signal spreads through atria → AV node (delays signal 0.1 sec to allow atria to contract first) → Bundle of His → Left and Right bundle branches → Purkinje fibers (rapid spread through ventricles). If SA node fails: AV node takes over at 40-60 bpm. If AV node fails: ventricles pace themselves at 20-40 bpm.

Arteries always carry blood AWAY from the heart — regardless of oxygen content. Veins always return blood TO the heart — regardless of oxygen content. The pulmonary arteries carry deoxygenated blood and the pulmonary veins carry oxygenated blood — this trips up many students. Capillaries are the site of gas and nutrient exchange — one cell thick. Arteries have thicker walls with more smooth muscle. Veins have thinner walls and valves to prevent backflow.

The heart supplies itself via coronary arteries that arise from the aortic root just above the aortic valve. Left coronary artery divides into the LAD (supplies anterior LV and interventricular septum) and Left Circumflex (LCx, supplies lateral and posterior LV). Right Coronary Artery (RCA) supplies the right heart and SA/AV nodes. LAD occlusion is called the "widow maker" because it causes massive anterior MI with high mortality.

Pericardium: double-walled fibrous sac surrounding the heart. Fibrous pericardium (outer) anchors heart. Serous pericardium has parietal and visceral layers with pericardial fluid between — reduces friction. Epicardium = visceral pericardium = outermost layer of heart wall. Myocardium: cardiac muscle — thickest layer, does the pumping work. Endocardium: smooth inner lining of chambers and valves. Cardiac tamponade = fluid compression in pericardial sac.

Pulmonary circulation: right heart → lungs → left heart. Short circuit, low pressure — only needs to push blood to the nearby lungs. Systemic circulation: left heart → entire body → right heart. Long circuit, high pressure — needs to push blood to the feet and back. This is why the left ventricle wall is 3× thicker than the right — it must generate far more pressure. Normal systolic BP = 120 mmHg (systemic). Pulmonary artery pressure = 25 mmHg.

P wave: atrial depolarization (atria contract). PR interval: conduction through AV node (delay). QRS complex: ventricular depolarization (ventricles contract) — atrial repolarization hidden here. T wave: ventricular repolarization (ventricles reset). ST segment elevation = STEMI (heart attack). Prolonged PR = heart block. Wide QRS = bundle branch block. Peaked T waves = hyperkalemia.

Blood pressure equals cardiac output times peripheral vascular resistance. Cardiac output = heart rate × stroke volume. Stroke volume depends on preload (filling), afterload (resistance), and contractility. Hypertension can result from increased CO (high HR or SV) or increased PVR (vasoconstriction). Baroreceptors in the carotid sinus and aortic arch detect BP changes and signal the medulla to adjust HR and vessel tone via the autonomic nervous system.