The Circulatory System

The Circulatory System

The circulatory system is one of the most important systems in the

human body. It consists of the heart and blood vessels. It is what

makes the blood in our body go round. The blood carries oxygen,

nutrients and hormones and takes them to where they are needed and

removes the waste products like carbon dioxide.

The circulatory system nourishes every cell, tissue, organ and organ

system in the body. There are approximately ten pints of blood

constantly circulating through seventy- five- thousand miles of blood

vessels. These blood vessels reach every cell in the human body. Once

they reach the cells they deliver much needed oxygen and remove carbon

dioxide and other poisonous waste products.

The circulation to and from the lungs is called the pulmonary

circulation; the circulation round the rest of the body is called the

systemic circulation. On average, a red cell would go round the whole

circulation in 45 seconds.

Our blood is pumped to two places: the right side of the heart pumps

blood to the lungs, and the left side of the heart has to work harder

pumping blood to the rest of the body which is why the left side of

the heart is bigger and more muscular than the right side. Blood is

pumped from the heart to the lungs and then travels back to the heart,

where it is then pumped to the body. To get all the way round the

circulation, blood has to go through the heart twice and this is why

it is known as a double circulation.

Blood is carried round all parts of the body by small tubes called

blood vessels. The human Circulatory system is composed of three types

of vessels; arteries, veins and capil...

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...ood and waste products back to the heart.

The blood in the veins moves slowly due to low pressure. Semi-lunar

valves are found at regular intervals throughout the veins. These

force the blood to move in only one direction. The veins walls are

thinner, wider, less elastic and less muscular than those of the

arteries. The veins are compressed when body muscles, particularly in

the limbs, move so the valves in the veins have to prevent the blood

flowing backwards. The blood in most veins is deoxygenated and

contains more carbon dioxide but less food than the blood in most

arteries. This is because respiring cells have used the oxygen and

food and produced carbon dioxide. The pulmonary veins, which return

blood from the lungs to the heart, are an exception. They contain

oxygenated blood and reduced level of carbon dioxide.