Exploring sport online: Athletes and efficient hearts

5.5 What is blood?

So, having learned about how blood moves around the body, let's now look at what it's made up of and therefore why we need it at all, and why its health has an effect on sporting performance.

Blood has four main components ? three types of cell and the watery liquid that holds these cells. Briefly, these four components are:

• Red blood cells these cells give blood its characteristic colour. They make up about seven per cent of blood and their main function is to carry oxygen molecules. The oxygen molecules attach to the red blood cells, and are carried around the body in the blood.
• White blood cells these are cells that make up about one per cent of blood. The main role of white blood cells is to fight infection. When there is a problem somewhere in the body, white blood cells in that area attack microbes such as bacteria or viruses and other impurities to try and stop the infection.
• Platelet cells these are cells whose main role is to create blood clots to help stop bleeding. When part of the blood flow system is broken (such as in a wound, both internal and external), these platelet cells move into the opening and block it, helping to stop more blood flowing out of the system.
• Blood plasma this is the watery liquid that carries the blood cells.

The blood is the body's main way of moving important material around. We've seen that oxygen is taken in through the lungs and gets to where it is needed by travelling in the blood, and this is carried along by red blood cells. The blood also carries nutrients around the body, once again by red blood cells.

The next section will combine what you've learned about the heart and blood by looking at the cardiovascular system, what we mean by an efficient cardiovascular system and how this affects athletes in a variety of sports.

Activity 7: What you need to do

You can click on some of the key terms or important words used in the text to see a short definition. All of these terms listed together are called a glossary.

Go back through the section and look at the terms we have included in our glossary. Were there any other terms that you would have included in our glossary? If so, have a go at creating a short definition for them and include them in your notes.

Discussion

How did you get on? You may have found that you weren't sure which terms to include. Compiling a glossary is another way of taking notes. If you come across any terms in this unit that you think are important and aren't already in the glossary you can add your own definitions to your notes.

Except for third party materials and otherwise stated (see terms and conditions), this content is made available under a Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Licence