Human Circulatory System

Chapter Overview

Human Circulatory System offers an in-depth examination of the cardiovascular apparatus and internal transport dynamics governing systemic fluid balance and tissue perfusion. The chapter starts with the gross and histological anatomy of the human heart: the fibrous and serous pericardium, epicardium, myocardium, and endocardium, the four muscular chambers, and the coordinated operation of atrioventricular (tricuspid and bicuspid/mitral) and semilunar (aortic and pulmonary) valves prevented from eversion by chordae tendineae and papillary muscles.

It thoroughly analyzes the cardiac cycle-tracing sequential atrial systole, ventricular systole, and complete cardiac diastole alongside corresponding heart sounds ("lub" from AV valve closure and "dub" from semilunar valve closure). Students study the intrinsic myogenic conduction system driven by the sinoatrial (SA) node pacemaker, atrioventricular (AV) node, Bundle of His, and Purkinje fibres, correlated with electrocardiogram (ECG) waveforms (P wave, QRS complex, and T wave). It also evaluates vascular hemodynamics: tunica adventitia, media, and intima differences across arteries, arterioles, capillaries, and veins, precapillary sphincter regulation, velocity changes, and arterial blood pressure measured via sphygmomanometry.

The concluding units cover circulatory pathways and pathologies. Students explore systemic, pulmonary, coronary, hepatic portal, and renal circuits. It outlines the pathogenesis of cardiovascular diseases (atherosclerosis, arterial plaque calcification, thrombus and embolus formation, myocardial infarction, and hypertension) along with modern clinical diagnostics and surgical treatments (coronary angiography, coronary artery bypass grafting, balloon angioplasty, and drug-eluting stenting). Finally, it investigates the lymphatic system-lymph capillaries, fluid filtration-reabsorption balance, lymph nodes, spleen, thymus, and lymphoid tissue roles in fluid return, fat transport, and adaptive immunity.