English Across the Curriculum


How Blood Works In The Body

The circulatory system carries blood to all parts of your body. The heart pumps blood through big blood vessels called arteries and veins. In our body there are also millions of small blood vessels called capillaries. Oxygen, food and other substances pass through the thin walls of these capillaries into the tissue.

When you inhale air oxygen passes through your lungs and and is picked up by haemoglobin which transports it to your whole body. It is released into cells which produce energy. In return, cells produce carbon dioxide, which enters your blood stream and is transported back to your lungs where it is exhaled.

Food also reaches your body by means of blood. It is digested in your stomach and important substances like fat, sugar, proteins, vitamins and minerals are separated. These nutrients enter your blood stream and are moved to the cells and muscles where they are needed in order to give you energy or fuel. The work of the muscles and other tissue creates heat. Blood is the transporting system which carries heat throughout your body and warms you. The things that you don't need are transported to your intestines and kidneys and leave your body again.

White blood cells play an important role in your immune system. When harmful substances invade your body an alarm goes off and white blood cells are activated. Then they work to destroy the invaders. They fight off viruses, harmful bacteria and begin anti-body production.

Blood also carries hormones to places where they are needed. When a hormone reaches a part of the body it controls growth, how the body uses food and other things.

You would bleed to death from a small cut if your blood didn't clot. When a blood vessel breaks platelets rush to the damaged area and stick to one another , forming a plug.

The body's circulatory system
Image (modified) : Termininja, CC BY-SA 3.0, via Wikimedia Commons