Vein — Science definition
A vessel carrying blood back towards the heart, wider and thinner-walled, with valves preventing backflow at low pressure.
Where it is taught
- Circulatory & Respiratory Systems — Body Organization, Transport & Movement, Life Science & Scientific Inquiry, Grade 7
In use
It returns in a vein, which is wider, thinner-walled and carries valves to stop backflow in the low-pressure return.
Circulatory & Respiratory Systems
Questions using vein
Problem 1
A vessel carries blood from the heart toward the lungs. Is it an artery or vein under the directional definition?
Answer and explanation
It is an artery because it carries blood away from the heart, regardless of its oxygen content before lung exchange.
Response criteria
- Explain the relevant biological process accurately.
- Use the supplied evidence and show calculation steps with units where needed.
- Connect a labeled model or mechanism with the claim.
- State an assumption, evidence limitation, or useful next observation.