The tireless engine of our body

Risposta: The heart is a truly remarkable organ; it is capable of contracting 90,000–150,000 times a day, ensuring a continuous blood flow of around 7,000 litres over a 24-hour period. To compare it to a hydraulic mechanism would be a gross oversimplification. Consider that it is estimated that the heart is made up of 8–9 billion cells, of which 2–3 billion are cardiomyocytes – the cells responsible for contraction. This enormous number of individual cells forms the building blocks of the four chambers of the heart, which are separated from one another by dividing walls (the interatrial and interventricular septa) and by the atrioventricular valves. The septa ensure that the heart is divided into a right side, which pumps blood to the lungs, and a left side, which supplies the rest of the body with blood. The tricuspid and mitral atrioventricular valves separate the atria from the right and left ventricles respectively. The pulmonary and aortic valves, located downstream of the right and left ventricles respectively, together with the aforementioned atrioventricular valves, ensure that blood flows in only one direction. Blood from the right side of the heart is pumped towards the lungs, where it is enriched with oxygen and releases carbon dioxide. From the lungs, the blood returns to the left atrium and from there to the left ventricle, where it is ejected into the systemic circulation, supplying oxygen and nutrients to the rest of the body. In order to optimise resources, the volume of blood pumped into circulation by the heart corresponds exactly to the needs of each moment. The contraction of the heart’s 2–3 billion cardiomyocytes is perfectly synchronised thanks to specialised cells involved in the generation and conduction of electrical impulses, which make up the cardiac conduction system. Consider that all the cells of the ventricles fire in perfect sequence in about one-tenth of a second. Downstream from the heart, the arteries supplying each individual organ can dilate or constrict to ensure the correct amount of blood reaches each organ. During physical exertion, the muscles require a great deal of oxygen and nutrients and therefore draw a large proportion of the circulating blood to themselves. At rest, the heart pumps around 5 litres of blood per minute; by contrast, during a fast run, the volume of blood ejected by the heart can reach 25–30 litres per minute. During digestion, it is the digestive system that requires a large amount of blood; for this reason, one should not engage in intense physical activity after meals. The heart and arteries are governed by a complex neural network that ensures an unrivalled balance in meeting the body’s needs. Its activity is always proportionate to the needs of the moment, ensuring that requirements are met whilst avoiding unnecessary energy wastage and structural stress. This neural network, which forms part of the autonomic nervous system, functions almost entirely independently of our will. Physical exertion or emotion increases adrenergic tone, resulting in an accelerated heart rate and greater contractile force of the heart; blood pressure also rises as a result of the heart’s increased workload and the vasoconstriction of the arteries. Efficiency is far more important than power when one considers that the heart is capable of working tirelessly for more than 100 years without any opportunity for rest. Are there any man-made pumps with such durability and reliability?