Identify the four major vessels
Explain the route and function of the pulmonary artery, pulmonary vein, aorta and vena cava.
AS Level; Cambridge International Biology 9700, 2028–2030. Written practice is self-checked; microscope recognition, biological drawing and supervised practical competence require practical work, while human subject-teacher review remains pending.
Before you begin
- Know that mass transport moves substances between exchange surfaces and cells, and that diffusion occurs down a concentration or partial-pressure gradient.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which vessel returns blood from the lungs to the left atrium?
What you will learn
- State which heart chamber each named major vessel connects to
- Distinguish pulmonary and systemic vessel roles
Build the explanation
The pulmonary artery leaves the right ventricle and carries blood to the lungs. Pulmonary veins return blood from the lungs to the left atrium. The aorta leaves the left ventricle and carries blood into the systemic circulation. The vena cava returns blood from the systemic circulation to the right atrium. These names are tied to the destination or direction of blood flow.
Apply it carefully
For examination explanations, pair each vessel with its route and the chamber at its heart end. In the normal adult model, the pulmonary artery carries relatively deoxygenated blood and the pulmonary vein carries oxygenated blood; these are exceptions to a common oxygen-content pattern, not to the definition of artery and vein. Do not assign oxygen content as the reason for the vessel's name.
Pause and explain
Which pairing is correct?
Worked example
Which vessel carries blood from the left ventricle into the systemic circulation?
Show the worked solution
- The vessel leaves the left ventricle.
- It supplies the body circuit.
Answer The aorta.
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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 the four vessels to their routes: pulmonary artery, pulmonary vein, aorta, vena cava.
Give me a hint
Use the heart chamber at the beginning or end of each route.
Compare my reasoning
- Right ventricle to lungs: pulmonary artery; lungs to left atrium: pulmonary vein.
- Left ventricle to body: aorta; body to right atrium: vena cava.
Pulmonary artery: right ventricle → lungs; pulmonary vein: lungs → left atrium; aorta: left ventricle → body; vena cava: body → right atrium.
Look for these in your work
- All four routes correct
- Heart-side chamber correct
Blood with lower oxygen content leaves the heart for the lungs. Name its vessel and explain why it is an artery.
Give me a hint
The destination is the lungs; classification depends on direction.
Compare my reasoning
- It leaves the right ventricle in the pulmonary artery.
- It is an artery because it carries blood away from the heart.
It travels in the pulmonary artery from the right ventricle to the lungs. It is an artery because it carries blood away from the heart, even though the blood has lower oxygen content.
Look for these in your work
- Pulmonary artery identified
- Direction used to justify name
- Oxygen exception handled
A diagram has a vessel labelled 'vein' entering the left atrium from the lungs. What is its name, and what does it carry in the normal adult model?
Give me a hint
Identify the source before naming the vessel.
Compare my reasoning
- It returns from lungs to left atrium, so it is a pulmonary vein.
- It carries oxygenated blood to the left side.
It is a pulmonary vein, carrying oxygenated blood from the lungs to the left atrium in the normal adult circulation.
Look for these in your work
- Vessel named from route
- Normal oxygen content correct
Common mistakes
- Calling the pulmonary artery a vein because of oxygen content
- Calling the vena cava an artery because it is large
- Mixing up the vessel entering the left atrium with the aorta
What can you explain now?
Which vessel returns blood from the lungs to the left atrium?
Compare with the explanation
Pulmonary vein
Pulmonary veins carry blood from the lungs back to the left side of the heart.
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Make it stick
Name the destination and heart chamber connected to each of the four major vessels.
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