The structures of the heart
The heart is a muscular pump which pushes blood through blood vessels around the body to the various tissues, it is about the size of the individuals clenched fist & lies behind the sternum, just left of the centre and is positioned between the right & left lungs. The heart is formed of cardiac muscle which is a special kind of muscle known as myocardium and can only be found in the heart. An individual’s resting heart rate known as a resting pulse varies from person to person, and depends on factors such as age and fitness. A resting pulse of a health adult typically ranges between 60-80 beats per minute which is between 80 and 100 thousand beats every single day.
The heart is divided into two separate halves of the left & right sides, which are identified as the opposite when viewing images like the one above. The left and right sides both have different functions as you can see here represented by different colours. The right side of the heart represented in blue, receives deoxygenated blood from the body & pumps this blood to the lungs to be oxygenated, whereas the left side of the heart represented in red, receives oxygenated blood from the lungs, & pumps this blood to the body.
Each side of the heart is hollow & is sectioned into two smaller connected chambers, making four chambers in total. The two upper chambers of the heart receive incoming blood from the veins and are known as atria, which is Latin meaning ‘entrance’ or atrium if the are named individually. Blood is pumped from the atria into the lower chambers known as the ventricles, it is from the ventricles where the blood is pumped out of the arteries to its destination.
You can see that the left ventricle has a larger myocardium wall than the right ventricle. This is because the left side pumps its contents to the furthest parts of the body as the blood is oxygenated, whereas the right side only has to pump blood to the adjacent lungs which is close to the heart to be oxygenated – hence the smaller myocardium walls on this side.
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There are a number of different valves located in different areas around the heart, their purpose is to stop back flow of blood in the heart, maintaining a one way circuit around the heart. The atrioventricular or AV valves separate the atria & ventricles, they prevent the flow of blood back into the atria during ventricular contraction, which known as systole. These atrioventricular valves have separate names according to the number of cusps or flaps they have. The right atrioventricular valve has three cusps and is known as the tricuspid valve. The left atrioventricular valve has only two cusps and is therefore known as the bicuspid or often the mitral valve
The semilunar valves prevent the flow of blood back into the associated ventricles during ventricular relaxation, which is known as diastole. The semilunar valves also have separate names according to where they are placed. The right semilunar valve is on the deoxygenated side of the heart and is sending blood to the lungs, therefore this is known as the pulmonary valve. The left semilunar valve is on the oxygenated side of the heart and is sending blood to the body, therefore this is known as the Aortic valve.