Circulatory systems
A pump and a network
- Your body's cells all need oxygen and food, fast.
- The circulatory system delivers blood to every cell.
- It has three parts: a pump (the heart), blood vessels, and valves for one-way flow.
Practice
The three parts of the circulatory system are:
The system is a pump (heart) + a network of vessels + valves that keep blood flowing one way.
Single vs double circulation (Supplement)
- A fish has a single circulation: blood passes through the heart once each trip round the body.
- A mammal has a double circulation: blood passes through the heart twice — once on the way to the lungs, once on the way to the body.
- Advantage: blood is re-pumped at high pressure before going to the body, so oxygen is delivered quickly.
Practice
In a mammal's double circulation, blood passes through the heart:
Double circulation means blood goes through the heart twice — once to the lungs, once to the body.
Practice
A double circulation lets blood be re-pumped at high pressure before going to the body.
Re-pumping at high pressure makes blood travel faster, delivering oxygen quickly.
You've got it
Key idea
- circulatory system = pump (heart) + vessels + valves (one-way flow)
- fish = single circulation (heart once per trip); mammal = double (heart twice)
- double circulation lets blood be re-pumped at high pressure for fast delivery