The role of the heart is to pump blood (full of oxygen and nutrients) to all parts of the body (organs, muscles, bone and skin), via a network of arteries (carry blood to the body) and veins (carry blood back to the heart).
The normal human heart is about the size of a fist and weighs 250-350 grams, depending on sex and body size. It sits behind the breastbone (sternum) and slightly to the left.
Muscle (walls)
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The heart consists of four chambers; the upper two are the atria (receive blood) and the bottom two are the ventricles (eject blood)
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The right sided chambers receive oxygen poor blood from the body and pump it to the lungs
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The left sided chambers receive oxygen rich blood from the lungs and pump to the body
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There are four heart valves (mitral, aortic, tricuspid and pulmonary) that function as ‘one-way’ valves, preventing blood from going the wrong direction
Coronary arteries (plumbing)
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There are 3 main arteries that arise from the aorta (main blood vessel exiting the heart). These blood vessels supply the heart muscle with blood, with each artery supplying a different part of the heart muscle.
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The coronary arteries are:
Left main coronary artery – this branches into the:
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- Left anterior descending artery (LAD)
- Left circumflex artery (LCX)
Right coronary artery (RCA)
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Each of the main vessels has several smaller side branches
Electrical conduction system (wiring)
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The conduction system of the heart is a specialised group of cells and pathways responsible for carrying the ‘electrical signals’ to the heart muscle and ensuring that these muscles contract in a co-ordinated and organised way.
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There is a group of specialised cells located within the sinoatrial node, this functions as the heart’s internal pacemaker. These cells respond to the impulses from the brain, the body’s hormones (i.e. adrenaline) and medications.
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