The normal heart
On this page, you are provided with basic facts on the anatomy and functions of the normal heart. It is advisable that you get acquainted with these pieces of information first, before wanting to know more about the individual heart anomalies.The heart is a muscular organ which comprises four chambers. Its size is approximately the size of your clenched fist. It is located in the thoracic cavity (chest), behind and slightly to the left of the sternum. The two upper chambers of the heart are known as the atria (sing. atrium) while the two lower chambers are the ventricles. The atria and ventricles are divided into left and right by muscular structures known as the interatrial and interventricular septum, respectively.
The function of the heart is to pump blood to the body and lungs, thereby ensuring adequate supply of oxygen and nutrients to all body tissues and organs. Backward flow of blood into the heart is prevented by its numerous valves. There are four valves in the heart – the tricuspid valve which seperates the right atrium from the right ventricle, the pulmonary valve,seperating the right ventricle from the pulmonary artery, the mitral valve which is situated between the left atrium and the left ventricle and the aortic valve between the left ventricle and the aorta. The mitral valve has two leaflets, while the other valves have three leaflets each.
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1.
Superior vena cava 2.
Right atrium 3.
Right ventricle 4.
Inferior vena cava 5.
Aorta 6.
Pulmonary artery 7.
Pulmonary veins 8.
Left atrium 9.
Left ventricle 10.
Interventricular septum 11.
Pericardium 12.
Myocardium 13.
Endocardium |
BLOOD CIRCULATION AND SUPPLY
The heart is connected to five great vessels. The superior and inferior venae cavae return deoxygenated (blue) blood from the venous system to the right atrium, from where it flows through the tricuspid valve into the right ventricle and then into the lungs through the pulmonary artery. In the lungs, carbon dioxide is removed from the blood and replaced with oxygen. Oxygenated blood flows into the left atrium through four pulmonary veins, then through the mitral valve into the left ventricle from where it is ejected under high pressure through the aorta into the whole body.
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1.
Blood circulation in the head 2.
Bronchial tree 3.
Arterial blood circulation 4.
Peripherial circulation 5.
Circulation in body organs 6.
Venous circulation 7.
Pulmonary circulation |
THE HEART BEAT
The heart has its own conducting system which ensures constant contraction and thus its functioning as a pump. The main source of the automatic heart beat is known as the sino-atrial node and is located in the wall of the right atrium. The sino-atrial node generates an electric impulse which spreads onto the atria, then through the atrioventricular node onto the ventricles. This electric impulse causes the heart to contract (systole), ejecting blood from both ventricles into the lungs and the whole body. Contraction of the heart‘s ventricles is followed by their relaxation (diastole) which ensures that blood flows into them. The number of heart contractions per minute is known as the heart rate or frequency. Newborns and infants have a higher heart rate (100-170bpm) than older children and adults (70-100bpm).
1. Sinoatrial node
2.
Right atrium
3.
Atrioventricular node
4.
Tricuspid valve
5.
Right ventricle
6.
Papillary muscles
7. Myocardium