The Human Heart: Anatomy & Physiology of the Cardiovascular System

The Human Heart: Anatomy & Physiology of the Cardiovascular System

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  THE HUMAN HEART Anatomy& Physiology of the Cardiovascular System SATENDRA SATENDRA PRADHAN PRADHAN Assistant Professor Assistant Professor Department of Pharmacology
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  Heart The heart isa hollow, muscular, cone-shaped organ that acts as the body's pumping machine. It continuously pumps blood through the blood vessels to supply oxygen, the blood vessels to supply oxygen, nutrients, hormones, and other essential substances to all tissues and organs while removing carbon dioxide and metabolic wastes.
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  The Heart ata Glance 4 Chambers 4 Valves 3 Wall Layers ~5L Blood / min 100K Beats / day Key Facts • Located in the mediastinum, slightly left of center, between the lungs • Size of a closed fist — weighs approximately 250–350 g in adults • Enclosed in the pericardium (double-layered protective sac) • Divided into right side (pulmonary) and left side (systemic) by the septum • Generates its own electrical impulse via the SA node (natural pacemaker)
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  A N AT O M Y The Four Chambers RIGHT ATRIUM • Receives deoxygenated blood from the body via vena cava. • Thin-walled receiving chamber. LEFT ATRIUM • Receives oxygenated blood from lungs via pulmonary veins. • Smallest of the four chambers. ← ATRIA (Upper) → Thin-walled receiving chamber. RIGHT VENTRICLE • Pumps deoxygenated blood to lungs via pulmonary artery. • Thinner walls than left ventricle. Smallest of the four chambers. LEFT VENTRICLE • Pumps oxygenated blood to body via the aorta. • Thickest walls — highest pressure. ← SEPTUM → ← VENTRICLES (Lower) →
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  A N AT O M Y The Four Valves Tricuspid Valve Type: Atrioventricular (AV) Location: Between right atrium & right ventricle Leaflets: 3 leaflets (cusps) Prevents backflow from right ventricle to right Mitral (Bicuspid) Valve Type: Atrioventricular (AV) Location: Between left atrium & left ventricle Leaflets: 2 leaflets (cusps) Prevents backflow from left ventricle to left atrium Prevents backflow from right ventricle to right atrium during systole Pulmonary Valve Type: Semilunar Location: Between right ventricle & pulmonary artery Leaflets: 3 semi-lunar cusps Prevents backflow from pulmonary artery into right ventricle Prevents backflow from left ventricle to left atrium during systole Aortic Valve Type: Semilunar Location: Between left ventricle & aorta Leaflets: 3 semi-lunar cusps Prevents backflow from aorta into left ventricle after contraction
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  A N AT O M Y The Three Wall Layers Epicardium Myocardium Epicardium (Outer Layer) • Thin, smooth outer surface of heart wall • Also forms the visceral layer of the pericardium • Contains coronary blood vessels and fat • Secretes pericardial fluid to reduce friction Myocardium (Middle Layer) Endocardium Cavity Myocardium (Middle Layer) • Thickest layer — composed of cardiac muscle cells • Responsible for the pumping action of the heart • Left ventricular myocardium is thickest (systemic pressure) • Cells are striated, branched, and involuntary Endocardium (Inner Layer) • Thin endothelial lining of heart chambers • Covers the inner surface of all four chambers • Also covers the heart valves and chordae tendineae • Continuous with the endothelium of blood vessels
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  V A SC U L A R S Y S T E M Blood Vessels → Arteries Carry blood AWAY from the heart • Thick, elastic, muscular walls to withstand high pressure ← Veins Carry blood TOWARDS the heart • Thinner walls, larger lumen, lower pressure • Carry deoxygenated blood ⇌ Capillaries Site of gas & nutrient EXCHANGE • Microscopic vessels — one cell thick (endothelium only) • Connect arterioles to • Carry oxygenated blood (except pulmonary artery) • No valves — pressure keeps blood moving forward • Major: Aorta, pulmonary, carotid, femoral arteries • Branch into arterioles → capillaries • Carry deoxygenated blood (except pulmonary vein) • Contain one-way valves to prevent backflow • Major: Superior/inferior vena cava, pulmonary veins • Collect from venules ← capillaries • Connect arterioles to venules • O₂ and nutrients diffuse OUT to tissues • CO₂ and wastes diffuse IN from tissues • Enormous total surface area for efficient exchange
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  P H YS I O L O G Y Dual Circulatory System PULMONARY CIRCUIT Right Heart → Lungs → Left Heart 1 Deoxygenated blood enters Right Atrium via superior/inferior vena cava 2 Right Atrium → (tricuspid valve) → Right SYSTEMIC CIRCUIT Left Heart → Body → Right Heart 1 Oxygenated blood enters Left Atrium via pulmonary veins 2 Left Atrium → (mitral valve) → Left 2 Right Atrium → (tricuspid valve) → Right Ventricle 3 Right Ventricle pumps blood → (pulmonary valve) → Pulmonary Artery 4 Blood travels to the lungs — CO₂ released, O₂ absorbed 5 Oxygenated blood returns via Pulmonary Veins → Left Atrium 2 Left Atrium → (mitral valve) → Left Ventricle 3 Left Ventricle pumps blood → (aortic valve) → Aorta 4 Blood travels to all body tissues — O₂ delivered, CO₂ collected 5 Deoxygenated blood returns via Vena Cava → Right Atrium Both circuits operate simultaneously — the heart's right and left sides pump in parallel, maintaining continuous circulation.
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  P H YS I O L O G Y Cardiac Cycle & Key Concepts DIASTOLE Relaxation Phase • Chambers relax and fill with blood • Atria receive blood from veins • Mitral & tricuspid valves OPEN • Aortic & pulmonary valves CLOSED SYSTOLE Contraction Phase • Ventricles contract and eject blood • Pressure rises sharply in ventricles • Mitral & tricuspid valves CLOSE • Aortic & pulmonary valves OPEN • Aortic & pulmonary valves CLOSED • Heart fills passively + atrial contraction • Aortic & pulmonary valves OPEN • Blood ejected to lungs & body Key Physiological Values 60–100 bpm Heart Rate (rest) ~70 mL Stroke Volume ~5 L/min Cardiac Output 120/80 mmHg Blood Pressure Cardiac Output = Heart Rate × Stroke Volume
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  P H YS I O L O G Y Electrical Conduction System 1 SA Node Sinoatrial Node The natural pacemaker — located in the right atrium wall. Generates spontaneous electrical impulses at 60–100/min. Initiates every heartbeat. 2 AV Node Atrioventricular Node Located at the junction of atria and ventricles. Delays the signal (~0.1 sec) to allow atria to fully contract before ventricles fire. 3 Bundle of His AV Bundle Carries impulse from AV node into the interventricular septum. Divides into left and right bundle branches. 4 Bundle Branches Left & Right Travel down each side of the interventricular septum toward the apex. Deliver signal to Purkinje fibers. 5 Purkinje Fibers Ventricular walls Rapidly distribute the impulse throughout the ventricular myocardium, causing simultaneous contraction from apex upward. ECG waves: P = atrial depolarization • QRS = ventricular depolarization • T = ventricular repolarization
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  Summary Chambers 4 chambers —R/L atria receive blood; R/L ventricles pump it. Left ventricle has thickest walls. Valves 4 valves ensure one-directional flow. AV valves (tricuspid, mitral) + semilunar (pulmonary, aortic). Layers 3 wall layers: epicardium (outer), myocardium (muscle — pumping), endocardium (inner lining). lining). Vessels Arteries carry blood away; veins return it; capillaries exchange O₂, CO₂, nutrients, and wastes. Circulation Two circuits: pulmonary (heart ↔ lungs) and systemic (heart ↔ body) work simultaneously. Conduction SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers coordinates each beat.