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How The Heart Works

• The heart is a muscular pump made up of four chambers: the right and left atria and the right and left ventricles.
• The heart requires its own blood supply to keep it working efficiently.
• The pumping action of the four chambers is coordinated by electrical signals telling the heart when to contract (squeeze) and relax.
• A series of four valves keep the blood moving in the right direction.

In order for the heart to function properly, it needs all of the above to work efficiently.

Network of blood vessels

Blood is pumped around the body through a network of blood vessels:

• Arteries transport oxygen rich blood from the heart to all parts of the body. The arteries get smaller as they get further away from the heart.
• Capillaries are the smallest of blood vessels. They connect the smallest arteries to the smallest veins. This is where oxygen, carbon dioxide, nutrients and waste products are exchanged.
• Veins carry blood, lacking in oxygen, back towards the heart. The veins get bigger as they get nearer the heart.

Blood vessels have a layer of spiral muscle within their walls. This makes them able to widen or narrow depending on how much blood each part of the body requires. The action on these muscles is a very complex mechanism which is partly controlled by hormones.

Movement of blood through the heart

• Blood from the muscles and organs of the body enters the right side of the heart into the right atrium (1)
• It is then pumped into the right ventricle (2)
• From there the heart pumps the blood to the lungs, where it takes up oxygen and gets rid of the carbon dioxide it has been carrying (3)
• This oxygen rich blood then enters the left side of the heart into the left atrium (4)
• It is then pumped into the left ventricle (the strongest of the four chambers) (5)
• From there it is pumped into the aorta (largest blood vessel in the body) (6) to all parts of the body including the heart muscle itself

Blood Pressure

Blood pressure is the measurement of the pressure within the arteries. It plays a vital role in the way the heart delivers fresh blood, containing the oxygen and nutrients required throughout the body, to all the blood vessels.

In order for the blood to travel throughout the body, quickly enough, it has to be under pressure. This pressure is created by the relationship between three things:

• The heart's pumping action
• The size and stretchiness of the blood vessels
• The thickness of the blood itself

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