Did you know that your blood makes up about 7% of your total body weight?
The blood has loads of important jobs to do. Some of these include:
- transporting oxygen to our lungs
- transporting important nutrients to cells and tissues
- forming blood clots to prevent too much loss of blood
- fighting off bacteria and other pathogens to stop us from getting sick
- getting rid of waste products
- regulating our body temperature
The blood is made up of four components:
- Red blood cells
- White blood cells
Each of these components has a specific function. Let's explore these further.
Red blood cells (RBC)
Red blood cells give the blood its bright red colour. They contain a special protein called haemoglobin which helps to collect oxygen from the alveoli in your lungs and deliver it to the cells around your body.
Red blood cells have a biconcave shape (a bit like a doughnut) to give it a larger surface area – it makes it easier for oxygen to diffuse into the cell. Red blood cells don't have a nucleus, this makes room for more oxygen and also makes the cell more flexible allowing it to fit through small vessels in the body.
White blood cells
Unlike RBCs, white blood cells contain a nucleus so are much larger than red blood cells and are fewer in number. White blood cells protect the body from infection by engulfing invading pathogens. Some white blood cells produce something called antibodies which attach to the surface of pathogens, helping to identify pathogens to be destroyed.
Unlike red and white blood cells, platelets are not actual cells but fragments of cells. The main function is to clot blood at the site of a wound to prevent further bleeding. The platelets end up forming a scab over the wound which also prevents further infection by bacteria.
Plasma is the yellow liquid component of your blood. Its job is to carry the blood cells mentioned above along with other substances such as waste products like urea, which is transported from the kidneys to the bladder. Small, soluble products of digestion produced by the small intestine also move around the body in the plasma.
You can think of the plasma as the water that forms a river and the fishes, frogs and alligators as being the cells that are transported by the river!
In the following activity, you will recall the main components of the blood and their functions.