Healthy Life

You may not give much thought to the bead of blood that appears when you cut your finger or scrape your knee, but it comprises a complex mix of red cells, white cells, platelets, and plasma. A Mediclinic expert explains why blood is vital for the body.

It’s widely known that red blood cells are responsible for transporting oxygen from the lungs to tissues around the body, but blood function doesn’t end there, says Dr Danie Kotze, a clinical haematologist at Mediclinic Constantiaberg.

White blood cells are crucial for immunity

Dr Kotze explains that the white cells in your blood play a crucial role in immunity. There are five different types of white cells, the most common being neutrophils. “These are the large cells that attack bacteria and fungi. Then there are lymphocytes, the second most common white blood cells. They’re involved in destroying virally infected and cancer cells. Lymphocytes can also form into plasma cells, which reside in the bone marrow and produce antibodies against invading organisms. In addition, certain lymphocytes regulate and control the rest of the immune system.”

The three remaining cell types are monocytes (involved in chronic inflammation); basophils; and eosinophils, which fight allergies and parasite infections.

Blood contains other immune proteins that act as a first line of defence against invading microbes. The most important of these, antibodies, recognise and tag infectious agents to be destroyed by the cellular component of the immune system.

The role of plasma in your blood

The importance of blood is amplified by the many other roles it plays. Plasma – the thin, yellowish fluid that sometimes seeps from a wound – is what ensures you don’t bleed to death after a cut as it contains clotting factors that help establish a blood clot. Dr Kotze describes the process like this: “When a blood vessel is damaged, little cell fragments called platelets form a plug in the damaged blood vessel wall and activate the clotting factors.”

Of course, clots in other areas of the body could cause harm by cutting off blood flow – which is why blood also contains natural anticoagulant factors that prevent the clot from spreading beyond the damaged area.

When is blood transfusion necessary?

With the many functions that blood performs, it stands to reason that any serious loss of blood, such as following an accident or surgery, can cause anaemia. “As a result, the patient might need to undergo a blood transfusion,” Dr Kotze says. He adds that plasma protein (albumin) infusions are also given to people whose liver is unable to produce certain blood components, or those with bleeding disorders like haemophilia. Most emergency blood units are blood Group O (or blood group O negative for women who may have children), as this blood group is unlikely to trigger an immune response from the recipient.

Keeping your blood healthy

Dr Kotze advises having an annual blood count analysis to help detect chronic conditions like anaemia or chronic leukaemia. You may also request a blood count if you’ve noticed excessive bruising, abnormal bleeding, shortness of breath, severe fatigue, recurrent infections, or fever for no apparent reason.

To find a clinical haematologist near you, go to

Kotze, Danie
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