Category: Cardiac Anatomy & Physiology

Introduction The primitive atrium is a critical structure in early cardiac development. It arises from the cranial part of the primitive heart tube and contributes to the trabeculated parts of the mature atria, including the auricles. The primitive atrium also plays a pivotal role in atrial septation, forming the basis for interatrial communication and the…

Introduction The sinus venosus is a crucial posterior structure of the developing heart tube that serves as the initial collecting chamber for venous blood in the early embryo. It plays a central role in directing blood flow into the primitive atrium and contributes to the formation of several important adult structures, including the smooth part…

The human heart is an extraordinary organ, capable of rhythmic contraction that sustains blood flow throughout the body. The action potential (AP) of cardiac muscle is central to this function, serving as the electrical trigger for coordinated contraction. Unlike skeletal muscle, cardiac action potentials are long-lasting, exhibit automaticity in pacemaker cells, and involve unique ion…

Introduction Cardiac output (CO) and stroke volume (SV) are central concepts in cardiovascular physiology, representing the heart’s ability to supply oxygenated blood to meet the body’s metabolic demands. Cardiac output is defined as the volume of blood ejected by the heart per minute, whereas stroke volume is the volume ejected per beat. Together, these parameters…

Introduction The Frank–Starling law of the heart is a fundamental principle of cardiovascular physiology that describes how the stroke volume of the heart adjusts to changes in venous return. It asserts that the force of ventricular contraction is proportional to the initial length of cardiac muscle fibers (preload). This intrinsic property enables the heart to…

The pressure-volume (P-V) loop is a powerful graphical tool used in cardiology and physiology to analyze the mechanical function of the heart. It provides an integrated view of ventricular pressure, volume, and cardiac work throughout the cardiac cycle. By plotting ventricular pressure against ventricular volume in real time, P-V loops offer critical insights into contractility,…

Introduction Cardiac output (CO) and stroke volume (SV) are central concepts in cardiovascular physiology, representing the heart’s ability to supply oxygenated blood to meet the body’s metabolic demands. Cardiac output is defined as the volume of blood ejected by the heart per minute, whereas stroke volume is the volume ejected per beat. Together, these parameters…

Introduction Heart sounds are audible vibrations produced by the cardiac cycle, primarily generated by valve closure, blood flow, and myocardial movement. They are fundamental to cardiovascular assessment, providing critical information about heart function, valvular integrity, and hemodynamics. Traditionally, four heart sounds are recognized: S1, S2, S3, and S4, each reflecting specific phases of the cardiac…

The heart is a dynamic organ whose primary function is to pump blood efficiently throughout the body. This pumping occurs in a coordinated cycle known as the cardiac cycle, which consists of alternating phases of contraction (systole) and relaxation (diastole). Ventricular systole, in particular, is the period during which the ventricles contract, generating sufficient pressure…

Introduction Cardiac function is a sophisticated interplay of electrical excitation, mechanical contraction, and hemodynamic forces. Among the fundamental events in the cardiac cycle, atrial systole and ventricular filling are essential for ensuring efficient ventricular preload and optimizing cardiac output. These phases occur during diastole, when the ventricles relax and accommodate incoming blood. While often overlooked…