It is an odd and a half organ, located within the rib cage between the two lungs, in front of the esophagus and resting on the diaphragm, having a volume similar to that of a fist and its weight can vary between 300 and 500 grams in a adult individual. It has a function of pump, essential for the circulation of the blood and, therefore, for life; this function being regulated by the autonomic nervous system through the electrical conduction system of the heart, so we cannot regulate the pumping frequency voluntarily.
It is made up of striated muscles that are fed by heart or coronary vessels. For obvious reasons it is a hollow organ, divided into four cavities separated from each other, two by two; two atria and two ventricles, communicating through fibrous valves that allow the passage of blood in one direction, a series of vessels leave or arrive from these cavities or precede the circulation of the body, all cardiac cavities are covered by a layer made of elastic, soft, smooth and shiny tissue called the endocardium.
The right atrium is located above and to the left of the heart with thin walls that receive venous blood, with the superior and inferior vena cavae, and being separated from the left atrium that is located above and to the right of the heart, the veins flow into right and left lung cells that carry arterial blood, both separated by the mitral valve that has two closing blades. The right and left ventricles are large and thick-walled, pumping blood from the arterial system, the right is located lower left of the heart, with a more powerful musculature separated from the left ventricle by the interventricular septum, which makes the process of pumping venous blood to the pulmonary artery that comes from the right atrium; the left ventricle located at the bottom right of the heart, its function is the most important, since it must draw arterial blood from the left atrium, through the aortic valve, to the general circulation.
We cannot forget the myocardium, which is the wall of the heart formed by the striated muscle and which constitutes the entire organ, allowing contraction and functioning as a perfusion pump. The heart is attached to the walls that surround it by a fibrous membrane called the pericardium.
