Circulatory Systems
Biology: Cambridge International GCSE Supplement, topic 9.1.1
Circulatory Systems
All animals have circulatory systems to transport things around their bodies. These systems are made of blood vessels, a pump (the heart) and valves to stop blood moving in the wrong direction.
Single circulatory system
- Fish have what is known as a single circulatory system because blood only travels through the heart once in every circuit around the body.
Double circulatory system
- Mammals have a double circulatory system, where blood travels through the heart twice per circuit.
- Double circulatory systems get oxygenated blood to tissues (like muscles) that need it faster than single circulatory systems.
- The concentration gradient between the blood and cells is also better maintained in double circulatory systems, so substances are exchanged between the blood and body cells faster.
Test yourself on Circulatory Systems
How many times per circuit does blood pass through the heart of a fish?
Which of the following groups of organisms has a double circulatory system?