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4 important functions of blood

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We cannot live without blood. The red liquid in our veins and arteries performs a number of vital tasks for the body. In this article we tell you what blood is and exactly what you need it for.

What is blood?

Essentially, blood consists of four components: red blood cells, white blood cells, platelets and plasma.

Red blood cells

Red blood cells make up some 40 per cent of your blood. You have about 25 thousand billion of them altogether. These cells look like round discs and, as the name suggests, are what make your blood red.

White blood cells

You have far fewer white blood cells: “only” about 35 billion at any one time. They act as the “soldiers” of your body, protecting it against pathogens – the viruses, bacteria and other organisms which cause disease.


Platelets are also abundant in your blood. You normally have between 800 and 2,500 billion in your body.


Just under half of your blood – 45 per cent, to be exact – is made up of red and white blood cells and platelets. The rest consists of plasma, which in turn is 90 per cent water. The blood cells and platelets are suspended in the plasma, the main function of which is to carry them and other substances like proteins, vitamins and hormones around your body.

4 functions of blood

Blood performs a number of important roles that are essential to life. Each of the above components has its own tasks, and they work together to keep you healthy.

1. Distributing oxygen

The most important function of blood is to transport oxygen from your lungs to the rest of your body. In the lungs, red blood cells pick up inhaled oxygen molecules and carry them to other parts of the body, where they are released. Other cells in your body convert oxygen into carbon dioxide, which is carried back to the lungs by red blood cells so that you can then

breathe it out. Because your heart is pumping blood around your body all the time, this process of supplying oxygen and removing carbon dioxide is constant.

2. Distributing nutrients

Besides carrying oxygen and carbon dioxide, your blood also ensures that your tissues are supplied with nutrients. These are transported in your blood plasma to the places in your body where they are needed. The plasma also removes waste products, so that you can discharge them via your bowels or bladder.

3. Fighting pathogens

Blood, and in particular the white blood cells, also plays an important role in your defence against pathogens. As soon as a pathogen enters your body, the white blood cells attack it and try to render it harmless. If that defence fails or does not work fast enough, you fall ill.

4. Blood clotting

The platelets in your blood ensure that it coagulates (sets) quickly when you suffer a wound, so that the bleeding stops. They act not only when your skin is injured, but also when the wall of a blood vessel is damaged. The platelets form a scab on the wound, allowing the affected tissue to repair itself and preventing you from losing too much blood.

How much blood do you have?

Blood makes up roughly 7 per cent of an adult human body. A person weighing about 70 kilograms has 5-6 litres. A new-born baby, however, has only 300-400 millilitres of blood and a pregnant woman 6.5-7.5 litres.

Blood problems

Because blood performs such important functions in your body, any problems with it can have serious consequences.

Blood loss

If you lose a lot of blood, there are not enough red blood cells left to transport the oxygen you need. And without that your body’s cells and tissues cannot function properly. Severe blood loss can lead to organ failure. A transfusion is often required in order to restore the volume of blood to a healthy level.

Low blood cell or platelet count

Another potential problem is a shortage of red cells, white cells or platelets. A low white blood cell count means that your body cannot defend itself properly against pathogens. People with this condition therefore fall ill on a regular basis. A lack of platelets causes

wounds to bleed longer than they should – a particular problem if you have a large wound that is losing a lot of blood.

Blood poisoning

Blood poisoning (sepsis) is a serious illness that can kill you if not treated quickly. It is caused by an infection to which your body reacts so violently that an inflammatory response occurs in the blood itself. Within 8-24 hours of contracting the infection, a person with sepsis becomes dangerously ill. The symptoms include fever, diarrhoea, abdominal pain and drowsiness.


Bloedcellen. (2019, 11 juni). – Alles over Bloed & Bloedcellen ✓

Menselijk Lichaam. (z.d.). Menselijk Lichaam – Hier vind je alles over het menselijk lichaam!

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