The Heart

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The Heart

Assuming that your heart beats 70 times each minute of the 70 years that the average person lives, your heart will beat 2,577,204,000 times. Two and a half billion!

Even that is an underestimate! So what is this amazing organ?

The adult human heart weighs about a kilogram and has four cavities inside it. These 'chambers' are divided into two at the top called the atria (each is called an atrium) and two at the bottom, called the ventricles.

Structure of the heart

The diagram shows that the heart is in fact divided neatly in two down its middle so that each side has one atrium and one ventricle. Both the left and right sides of the heart pump blood. The only difference between them is where the blood arrives from and to where it is pumped.

The muscle that makes up the heart is unusual as it doesn't get tired while it pumps. But it can be damaged by drugs and poor diet leading to heart disease.

 heart in action
  1. Blood fills the atria and the bicuspid and tricuspid valves are closed.
  2. The atria gently contract and push their blood into the two ventricles.
  3. The ventricles start to contract, this closes the atrioventricular valves (the bicuspid and tricuspid valves) and pushes the blood out through the semi-lunar valves into the pulmonary artery and the aorta.

Both sides of the heart beat in sequence together but the blood they pump goes to different locations. The left ventricle pumps blood to all of the body whereas the right ventricle pumps blood to the lungs from where it returns to the left side of the heart.

Each time the ventricles pump you can feel a great wave of blood moving along the arteries. This can be felt and gives an idea about how the heart acts.

If you listen to the heart with a stethoscope you hear two sounds which are described as being 'lub' and 'dub'. The first is the sound made by the two atrial valves closing, whilst the second is caused by the two semi-lunar valves closing.

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