Connect the pump, vessels and valves in a circulatory system
Explain how three parts work together to keep blood moving in a directed pathway.
Mapped to the named 0654 section using teaching from the corresponding single-science course. A 0654-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall muscles, organs and transport.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which structure actively generates pressure by contraction?
What you will learn
- A pump creates a pressure difference
- Valves limit backward movement
A pump creates a pressure difference
A circulatory system moves blood through blood vessels. The heart is a muscular pump: contraction raises pressure and pushes blood into vessels. A vessel provides a route, but its mere presence does not continually drive blood around the system.
Blood carries materials between organs and tissues. Transporting a substance is different from making it: a heart does not manufacture oxygen, and oxygen enters blood at a gas-exchange surface. Connect each part to its role rather than giving every part the same function.
Valves limit backward movement
Valves help ensure one-way flow by opening for movement in the permitted direction and closing when pressure would otherwise push blood backwards. A valve is a control on direction, not a second pump or an oxygen filter.
In an explanation, link muscular contraction to a pressure difference, vessels to a transport pathway, and valves to prevention of backflow. Not every vessel contains valves; the requirement is that the system has valves at relevant positions, including the heart and many veins.
Sources for this lesson
Pause and explain
Which pairing gives each part its own role?
Worked example
Explain why a system with vessels but no effective pump or valves may not maintain directed circulation.
Show the worked solution
- Without an effective pump, there is no sustained pressure-producing contraction.
- Without effective valves, backward movement can occur when pressure reverses.
Answer Vessels provide the route; a muscular pump produces pressure and valves prevent backflow at relevant sites.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Match heart, vessels and valves to pressure, pathway and prevention of backflow.
Give me a hint
Match a function to the structure that performs it.
Compare my reasoning
- Heart contraction produces pressure.
- Vessels provide a pathway; valves prevent backflow.
Heart → pressure; vessels → pathway; valves → prevent backflow.
Look for these in your work
- Assign all three functions
- Separate pumping from valve action
Improve “blood vessels pump blood and the heart stops it going backwards”.
Give me a hint
Swap the incorrectly assigned roles.
Compare my reasoning
- The muscular heart is the pump.
- Relevant valves, not the whole heart as a single stop, prevent backward movement.
The heart pumps blood through vessels; valves at relevant sites prevent backflow.
Look for these in your work
- Identify the muscular pump
- State the role of valves
A flexible tube is attached to a working pump but its valve fails to close. Why can forward pumping coexist with inefficient circulation?
Give me a hint
Consider what happens when the pressure difference reverses.
Compare my reasoning
- The working pump can still generate forward pressure.
- A leaking valve permits backward movement, reducing effective directed transport.
Forward pumping can occur, but backflow through the failed valve reduces effective one-way circulation.
Look for these in your work
- Retain the working pump
- Explain backflow without inventing oxygen production
Common mistakes
- Calling valves pumps.
- Claiming all blood vessels contain valves.
What can you explain now?
Which pairing gives each part its own role?
Compare with the explanation
Pump: pressure; vessels: route; valves: prevent backflow
The roles work together.
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Make it stick
Explain circulation using three distinct verbs: pump, carry and prevent.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.