The heart is the engine of our body and is essential for blood circulation. An organ necessary for conveying oxygen taken from the lungs to the cells, organs and tissues of the human body to feed them, it is responsible for the exchange of carbon dioxide, which represents the waste of the metabolic cycle.
What is the heart?
It is a muscular organ divided into two cavities, right and left, both having an atrium and a ventricle; these are arranged vertically and are isolated from each other by walls called septa. In an adult human the weight of the heart reaches up to 250-300 g, while in newborns it weighs approximately 20-21 g.
What is the heart made up of?
It is located in the center of the chest slightly shifted to the left; protected by the sternum, it rests on the diaphragm. It resembles a conical shape and is the result of the overlapping of tissues such as:
- the pericardial sac, in which it is wrapped;
- the epicardium;
- the heart muscle, or myocardium;
- the endocardium, which represents the inner lining of the heart.
Its muscular tissue, made up of voluntary muscles – unlike other muscles in the human body – autonomously generates the nervous stimulus that ensures its beat.
More specifically, the myocardium is made up of cardiac cells and muscle fibers called myocardiocytes. They ensure that the nerve impulse arrives, which is essential for the heartbeat, thus allowing blood circulation.
The impulse that generates the contraction movement of the heart, by means of the muscle fibers, starts from the sinoatrial node, which is located between the superior vena cava and the right atrium. The vagus nerve together with the sympathetic fibers, ensure the coordinated functioning of the heart with cerebral stimuli, connecting the organ with the sensitive, sympathetic and parasympathetic systems; other autonomous fibers constitute the cardiac plexus.
The heart is made up of four valves: the tricuspid and mitral valves form the atrioventricular valve, which is necessary to control and regulate blood flow between the atria and ventricles. Two other valves – the pulmonary valve and the aortic valve (together called semilunar valves) – connect the heart and the blood vessels.
The heart is in direct communication with the blood vessels in order to obtain – from the tissues and organs – oxygen and return carbon dioxide. The conductors of blood loaded with carbon dioxide are two veins: the inferior vena cava and the superior vena cava, which connect the tissues to the heart. The blood necessary for the flow between the heart and the lungs is managed by the pulmonary artery and the pulmonary vein. The aorta, which is the main artery of our body, distributes the blood loaded with oxygen throughout the body.
Composition of the heart:
- Right atrium
- Left atrium
- Right ventricle
- Left ventricle
- Aortic valve
- Mitral valve
- Pulmonary valve
- Tricuspid valve
What does the heart guarantee?
The primary function of the heart is to circulate blood throughout our body; from organs to cells and tissues, meeting their demand for oxygen. At the same time, it has the task of taking and carrying back to the lungs the carbon dioxide to be expelled.
Through the aorta, blood travels throughout the body together with oxygen; this is called arterial blood. It nourishes the body, reaching every tissue and dividing into capillaries of increasingly smaller size. The blood rich in carbon dioxide – the fruit of cellular work – instead returns to the heart through the vena cava. In the daily course of ordinary life, the heart supplies the body with 5 liters of blood per minute; in full physical activity, we are talking about 20 or 30 liters of blood loaded with oxygen per minute. The correct pressure ratio to aim for is between 130 systolic (high) and 80 diastolic (low) mmHg.
The cardiac cycle is the work that the heart does: it is the succession of two repeated movements, systole and diastole, which are repeated – at rest – for about 70/80 times per minute. Systole is the phase of contraction, while diastole is the phase of relaxation. Their continuous work allows to maintain the blood pressure in the cardiac areas, providing for their closure in order to avoid retrograde flow.
In the diastole phase the valves open, the muscles relax so that the blood flows into the chambers between the atria and ventricles. At the same time the semilunar valves remain closed, so that the blood cannot circulate in the vascular beds.
In the systole phase, the opposite happens: in a coordinated movement, the atria and ventricles contract. The pressure that is created pushes the blood towards the atrioventricular valves, causing them to close. At this point, the blood, unable to return to the atria, is pushed into the veins, thus entering circulation.
The coronary arteries have the task of keeping the heart active, pushing inside it – into the heart muscle – blood loaded with oxygen. If the myocardium does not receive enough blood due to certain factors (for example, narrowing of the coronary arteries or other roughness), the heart and its entire apparatus would suffer from lack of oxygenation.
When we talk about ischemic heart disease or myocardial ischemia, we are referring to acute coronary syndrome or more simply myocardial infarction. Pathologies and other problems related to the heart muscle can also be: lesions to the valves, inflammation or problems related to nerve conductions that lead to arrhythmia.