The circulatory system isn’t just about the heart. The heart would not be able to do its job without a massive network of blood vessels. These ensure that the blood gets to every single cell in your body. This network is so long that if all of the vessels were stretched out in a line, they would be more than 60,000 miles long. This is equivalent to travelling more than twice around the globe!!!
Your heart beats at around 70 times per minute, and with each beat pumps 60 – 90ml of blood. This equates to up to 7 litres of blood per minute and 7600 litres per day. In other words, a staggering 200 million litres of blood in a lifetime! The blood vessels are also an important defense mechanism for your brain, known as the blood-brain barrier. This barrier, consisting of blood vessels and tissue containing cells spaced close together prevents harmful substances reaching your brain.
It is your blood vessels which are responsible for brain freeze! When you eat something really cold, and it touches the roof of your mouth, blood vessels constrict to minimize heat loss. The same vessels then relax to restore the flow of blood. It is this response which triggers the sharp pain in your head!
GCSE biologists, if you need help with understanding the blood, and blood vessels, try our new guide “How to work with the Circulatory System: Part 2”. It includes a description of the main parts of the blood, their functions, and the difference between arteries, veins and capillaries. There are questions and answers included.
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