Heart Medical Science Low-poly 3D model

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Blood carries oxygen and nutrients while eliminating waste in humans; the heart, situated between lungs in chest's middle compartment, is divided into four chambers - left and right atria and ventricles. In contrast, fish have two-chambered hearts and reptiles possess three-chambered ones. Healthy one-way blood flow in the heart is facilitated by valves, while the pericardium protects it and contains a small amount of fluid. The heart's wall consists of three layers: epicardium, myocardium, and endocardium. Its rhythm is determined by pacemaking cells within the sinoatrial node, which travels through the conduction system. Blood low in oxygen enters from superior and inferior venae cavae, passes to right ventricle, moves into pulmonary circulation for oxygenation, returns to left atrium, then left ventricle, and is pumped out via aorta to systemic circulation for use of oxygen.[1-9] Exercise temporarily increases heart rate but lowers resting rate in long term, benefiting heart health.