Heart
The heart is a hollow, muscular organ about the size of a fist, located in the middle mediastinum. The weight of an adult heart is about 300 g. During the day, it makes more than 100,000 contractions, pumping about 7,000 liters of blood. Over 70 years of life - more than 2.5 billion blows.
Chambers of the heart
The heart consists of four chambers:
- Right atrium - receives venous blood from the superior and inferior vena cava
- Right ventricle - pushes blood into the pulmonary trunk (pulmonary circulation)
- Left atrium - receives arterial blood from the pulmonary veins
- Left ventricle - pushes blood into the aorta (large circle)
The wall of the left ventricle is 3 times thicker than the right one because it must create enough pressure to supply blood to the entire body.
Valve apparatus
Four valves ensure unidirectional blood flow:
| Valve | Location | Type |
|---|---|---|
| Tricuspid | Between the right atrium and ventricle | Casement |
| Mitral | Between the left atrium and ventricle | Casement |
| Pulmonary | Output from the right ventricle | Lunar |
| Aortic | Output from the left ventricle | Lunar |
The sounds of valves closing are the heart sounds heard with a stethoscope.
Conductive system
The heart has its own electrical system:
- Sinoatrial node (pacemaker) - generates 60–80 impulses per minute
- Atrioventricular node - delays the impulse by 0.1 s (so that the atria have time to contract)
- Bundle of His - conducts impulses to the ventricles
- Purkinje fibers - distribute impulses throughout the ventricular myocardium
This system is autonomous - the isolated heart continues to beat. On the ECG, each impulse is reflected by a characteristic curve: P wave (atria), QRS complex (ventricles), T wave (repolarization).
Coronary blood supply
The heart is fed through the coronary arteries - right and left. The left is divided into the anterior interventricular and circumflex branches. Blockage of a coronary artery by a blood clot leads to myocardial infarction - death of a section of the heart muscle.
Knowledge of the anatomy of the coronary vessels is critical for cardiac surgeons when performing stenting and coronary artery bypass grafting.
Do you want to see the chambers, valves and coronary vessels in volume? A detailed interactive model of the heart is available in the 3D atlas Humio.