Vein

In the syllabus and the exam

Vein questions extend the artery-versus-vein comparison by focusing on how a low-pressure vessel still manages to return blood efficiently to the heart against gravity, especially from the limbs. Candidates should explain that a vein has a thinner wall with less muscle and elastic tissue because it carries blood at low pressure, a wider lumen that offers less resistance to slow-moving blood, and valves at intervals that prevent backflow, working together with the squeezing action of surrounding skeletal muscles during movement. An SPM-style extended question might ask why someone who stands still for long periods can feel swelling in the legs, and a strong answer links reduced muscle-pump activity to blood pooling in the veins despite functioning valves. Students frequently confuse a thin wall with a weak vessel, when the correct reasoning is that veins do not need a thick wall because they are not exposed to the pressure surges that arteries must withstand.

Example

Valves inside a vein snap shut between heartbeats to stop blood sinking back down under gravity in the legs.

Related terms

ArteryCapillaryDouble circulation

Source:SRC-DSKP-EN