Education: importance of blood

You’ve stubbed your toe and it’s bleeding – will it stop? Of course it will. But how does it know how to do that and can your body make more blood?

BLOOD is a highly specialised bodily fluid that works like a fleet of delivery vans: it collects essential substances such as oxygen, sugar and hormones in one area of your body and delivers them to cells that need them. It also takes waste products, such as carbon dioxide, to the body’s “garbage bin” so they can be removed from the body. Blood also helps to protect you against disease. Arteries transport oxygen-rich blood from your heart to the rest of your body, while veins transport oxygen-depleted blood to the heart. The average person has four to six litres of blood. But what’s blood, and where does it come from?

HOW DOES YOUR BODY MAKE BLOOD?

Although blood isn’t produced in a kitchen, it’s made according to a recipe from a long list of ingredients. To make blood, your body combines red blood cells, white blood cells, platelets and plasma. Your body has to manufacture all these “ingredients” itself. Red and white blood cells and platelets are made by your bone marrow, a jelly-like substance that

RED BLOOD CELLS

These cells are small so they can move through narrow blood vessels known as capillaries. They look almost like deflated soccer balls. This shape increases the surface area of the cell so it can carry lots of oxygen to distribute it more quickly. Red blood cells also contain haemoglobin, a special kind of protein

containing iron that absorbs oxygen in your lungs and releases it in the rest of your body.

WHITE BLOOD CELLS

White blood cells are part of your immune system: they defend the body against infections. These cells are able to move in and out of your bloodstream to reach parts of the body where they’re needed. White blood cells also help fight abnormal cells in your body, such as cancer.

PLASMA

Plasma transports solutions such as hormones and antibodies; nutrients like water, glucose and amino acids; and minerals and vitamins to where they’re needed in the body. It also takes waste products such as carbon dioxide to where they can be excreted. Just

more than half your blood, about 55 percent, is made up of plasma. PLATELETS

Platelets help your blood to clot. When you cut your finger or bump your toe and it bleeds, the platelets in your blood bind together to form a blood clot that stops the bleeding. This is what happens when that scab forms where you’ve gashed your knee.

THE FUNCTIONS OF BLOOD IN THE BODY

It transports oxygen to your cells. It supplies essential nutrients such as amino acids, fatty acids and glucose (sugar) to the cells. It removes carbon dioxide and other waste products from your body. It transports hormones from your brain to the rest of your body. It regulates acid levels in your body. White blood cells protect you against infections and dangerous cells. Platelets help your blood to clot when you bleed. Blood also helps regulate body temperature. Do your cheeks turn red after you’ve run some distance? That’s because more blood flows to your skin after exercise so it can

help to cool you down more quickly as heat is lost to the air. And when it’s cold outside blood flows to your vital organs deep inside your body to keep them warm. BLOOD GROUPS

Do you know which blood group you belong to? We all belong to one of four blood groups (O,B, A or AB), which are divided into eight sub-groups: O-, O+, B-, B+, A-, A+, AB- or AB+. When someone is injured in an accident and loses a lot of blood, they need a transfusion of blood donated by another person. But you can’t just be given any blood – doctors have to check whether your body will accept or reject the donated blood.

That’s why the recipient’s blood is screened and typed before a blood transfusion. Doctors also first test how your body reacts to the donor blood to make sure the recipient doesn’t develop a negative reaction after the blood transfusion, which could be life-threatening.

If your blood group is O, your blood can be donated to people of virtually all other blood groups, but you can receive blood only from your own group. If you’re in group A you may get blood only from groups A and O and if you’re group B you may get blood only from groups B and O. If you’re AB, you can accept blood from most other blood groups.

Red blood cells look almost like deflated soccer balls. They’re one of the “ingredients” of your blood. White blood cells are almost like bodyguards in your body – they protect you against disease and rogue cells like cancer cells.

Blood pressure is a measurement of how hard your blood presses against the walls of your blood vessels. The pressure in blood pumped from the heart to the rest of your body is much higher than in blood flowing back to the heart.

The human body can’t function without blood. When someone has lost a lot of blood, for example when injured in a car accident, a blood transfusion could save their life (BELOW). Without blood donors (LEFT) transfusions wouldn't be possible.

When a blood vessel breaks it starts to bleed. To prevent blood loss, blood cells called platelets stick to the damaged area and to one another, forming a plug.