Heart: Structure
The human heart is a strong, cone-shaped hollow muscle with a rounded tip. In an adult, the heart muscle is about the size of a fist and weighs an average of 250 to 300 grams. As a rule, a woman’s heart is slightly lighter than a man’s. The critical heart weight starts at about 500 grams. Heavier hearts can hardly be properly supplied with blood and enough oxygen. There is a risk of a heart attack.
The heart undoubtedly plays an important role in the human body. Without blood vessels, however, it would be powerless: the arteries and veins transport the blood set in motion by the heart throughout the body.
Anatomically, the human heart does not look like the classic red heart that is usually drawn. It is not symmetrical, for example, because the left and right halves of the heart are different sizes. The left ventricle has a very thick wall because it has to pump blood throughout the body. In addition, there is no indentation in the upper center as in the painted heart.
Atria and ventricles
The heart structure is adapted to the complex function of the organ as the “engine” of blood circulation. The cardiac septum divides the hollow muscle into left and right halves. Each half is again divided into two compartments: left and right atrium and left and right ventricle.
From the outside, the division into atria and ventricles can be recognized by the so-called coronary groove. This is a ring-shaped depression (sulcus coronarius). From here, further cardiac grooves extend toward the apex of the heart. These depressions, the so-called sulci interventriculares, show from the outside where the cardiac septum lies on the inside. The coronary vessels, which are also called coronary arteries, coronaries or coronary vessels, run in the cardiac grooves.
Heart ears
It is not yet known exactly what function the heart ears have. What is clear, however, is that they produce an important protein: ANP (atrial natriuretic peptide). This messenger substance regulates the salt and water balance and in this way also the blood pressure.
Cardiac skeleton
Heart valves
How many valves the heart has is easy to answer: four. There is always one valve between the atrium and the ventricle – on the left and on the right side. This already gives two valves. In addition, there are valves between the ventricles and the blood circuits – the small and the large. This gives a total of four valves in the heart, which work like valves.
At the upper end of the heart muscle, the base of the heart, the large vessels leave: the pulmonary artery (arteria pulmonalis), which supplies the pulmonary circulation (small blood circulation), leaves from the right chamber. Here, the pulmonary valve is interposed to ensure that blood does not flow back into the right ventricle.
Heart wall layers
Not visible to the naked eye are the three layers of the heart wall. From the outside in, these are:
- Epicardium (outer layer of the heart, part of the pericardium)
- Myocardium (layer of heart muscle)
- Endocardium (inner layer of the heart)
Heart: location in the body
Where is the heart located in the body? In common parlance, the answer to this question is usually: on the left. This is not correct. But where exactly is the heart located – on the left or on the right? The answer is: the heart is located in the center of the chest.
The position of the heart in the thorax provides the organ with special protection. This is because the spinal column lies behind the heart. At the sides and front, it is protectively surrounded by the ribs and sternum.
The position of a woman’s heart does not differ from that of a man’s heart. The anatomical heart has the same structure in all sexes. Its position is also not influenced by gender.
On which side is the heart?
The heart and its neighboring organs
Heart: function
What exactly does the heart do and what are the functions of the organ? The function of the heart is the movement of blood in the circulatory system, more precisely in the small and large blood circulation. The body’s engine acts like a pressure and suction pump. The various valves work like valves that regulate the flow of blood. They ensure that the blood is always pumped in the right direction and does not flow back.
The blood flows through the heart in this order:
- left atrium – left ventricle – systemic circulation.
The cycle then starts all over again.
In one day, the heart thus transports several thousand liters of blood through the body. The amount of blood in the human body is about 5 liters. This blood is pumped through the entire body several times a day. With each beat, the heart transports about 70 to 80 milliliters. This means that – depending on the heart rate – it transports about five to six liters of blood per minute.
Via the AV node, which is a switching point between the atria and the ventricles, the signal then reaches the ventricles, which also contract – the heart “pumps”. These excitation waves can be visualized in an ECG (electrocardiogram).
If the pulses work well, a heart rate is produced. It is also known as the pulse. How often the heart beats per minute is called the heart rate. At rest, the heart rate for an adult is about 60 to 80 beats per minute. During exertion, this value increases. Then 150 to 200 beats per minute are conceivable.
Coronary arteries
The heart has arteries that lead away from the heart to supply the body. But it also has arteries that supply blood to the heart itself. The heart keeps itself alive, so to speak – pumping vital blood to a body of which it is itself a part. The vessels that supply the heart itself are called coronary vessels. They supply the organ with important nutrients and oxygen.
Pericardium
The pericardium is a tissue envelope in which the heart moves. This pericardium consists of two layers: an inner layer (epicardium) and an outer layer. The outer layer is the pericardium proper. Between the two layers is a type of fluid that allows the heart muscle to move and expand smoothly.
You can read more about this pericardium in our article Pericardium.
Myocardium
Read more about the working muscles of the heart and their function in our article Myocardium.
What problems can cause the heart?
If the heart, i.e. the hollow muscle, does not contract in an orderly manner, cardiac arrhythmias are present. The most common forms include atrial fibrillation and atrial flutter. If people have a severely slowed heartbeat, this is called bradycardia. The opposite is palpitations, medically called tachycardia.
The heart valves can leak from birth or become leaky during life. This is called insufficiency. In the case of a severe heart valve defect, they no longer close or open properly. As a result, blood flows back into the atrium or ventricle or is no longer transported properly. Sometimes those affected then need an artificial heart valve.
In addition, various pathogens can attack the heart. In the course of a viral or bacterial infection, there is a risk of inflammation of the heart muscle (myocarditis), especially if patients do not take it easy on themselves, or of inflammation of the inner lining of the heart (endocarditis). Patients with artificial heart valves or severe heart defects are particularly at risk.
