The anatomy of the heart is such that there are four main vessels through which blood enters and leaves the organ to circulate the body. These are the inferior and superior vena cava, the aorta, the pulmonary artery and veins, and the coronary arteries. These arteries are responsible for blood supply to heart muscles, while the pulmonary artery transports blood that has little oxygen from the heart into the lungs for oxygenation (Low et al., 2020). The pulmonary veins then bring the blood that has been oxygenated back to the heart. The heart, however, functions independently of any executive control exerted to it by the brain. This is the concept of automaticity where heart cells in the regions of the SAN, AVN, and His-Purkinje conduction system generate action potentials by spontaneous depolarization (Vetulli et al., 2018).
On the other hand, as blood flows through the cardiac chambers as well as valves open and close, vibrations of the heart structures create audible sounds, especially when blood flow is highly turbulent (Dornbush & Turnquest, 2019). Some of these heart sounds are pathological indicators of pathophysiological conditions, hence making diagnosis easy. In systole, the mitral and tricuspid valves close, resulting in hemodynamic changes that create vibrations that are referred to as S1 heart sounds. (Dornbush & Turnquest, 2019). When aortic and pulmonic valves close in diastole, on the other hand, S2 sounds are created. Unlike S1, S2 sounds are easily discernible as the increased volume takes the right ventricle longer to pump blood out, thus delaying the pressure growth that results in the closure of the pulmonic valve. Besides, S2 sounds provide a lot more useful clinical and diagnostic information, especially its role as the auscultatory ancho point (Dornbush & Turnquest, 2019).
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Other diastolic murmurs with clinical and diagnostic significance are the S3 and S4 sounds. For instance, though there is controversy over the mechanisms that create S3 sounds, classical teachings claimed that the sounds were created during an acute heart failure exacerbation (Dornbush & Turnquest, 2019). On the other hand, S4 sounds are created by a less compliant ventricle and are the main clinical and diagnostic marker for diseases like left ventricular hypertrophy. Overall, heart sounds are essential clinical and diagnostic tools as they not only save time, costs but do not risk patient safety.
References
Dornbush, S., & Turnquest, A. E. (2019). Physiology, Heart Sounds. In StatPearls [Internet] . StatPearls Publishing.
Low, D. A., Jones, H., Cable, N. T., Alexander, L. M., & Kenney, W. L. (2020). Historical reviews of the assessment of human cardiovascular function: interrogation and understanding of the control of skin blood flow. European journal of applied physiology , 120 (1), 1-16.
Vetulli, H. M., Elizari, M. V., Naccarelli, G. V., & Gonzalez, M. D. (2018). Cardiac automaticity: basic concepts and clinical observations. Journal of Interventional Cardiac Electrophysiology , 52 (3), 263-270.
