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GCSE Biology · key term
A structure that allows blood to flow in one direction and prevents it from flowing backwards.
Used by Edexcel and OCR
Specification 8.7, 8.8 · Paper 2
Revise: Blood VesselsMany veins also contain valves. These open as blood moves towards the heart and close if it starts to flow backwards, helping to keep the low-pressure blood moving in the right direction.
A structure that prevents blood flowing backwards, keeping it moving in one direction.
Specification B2.2d · Paper 1 (Foundation), Paper 3 (Higher)
A structure that permits flow in one direction and prevents backflow.
Revise: Heart and blood vesselsThe mammalian heart keeps blood moving through blood vessels so that this transport can happen. Its structure is matched to this demanding function: it is made from cardiac muscle, contains four chambers and has valves that maintain one-way flow.
Paper 1 (Foundation), Paper 2 (Foundation), Paper 3 (Higher), Paper 4 (Higher)
A structure that allows blood to flow forwards but prevents it flowing backwards.
Revise: Heart StructureThe heart is an organ that pumps blood through blood vessels. This keeps blood moving so that cells can receive substances such as oxygen and dissolved food molecules, while wastes can be carried away. Its structure suits a repeated pumping job: cardiac muscle provides the force, chambers receive and eject blood, and valves keep it moving in the intended direction.
A structure that opens to allow forward flow and closes to prevent backflow.
Trace blood as one continuous route rather than memorising isolated labels: vena cava → right atrium → tricuspid valve → right ventricle → pulmonary semilunar valve → pulmonary artery → lungs → pulmonary veins → left atrium → bicuspid valve → left ventricle → aortic semilunar valve → aorta.
Valves prevent backflow; they do not pump blood. They open and close because of pressure differences on their two sides.
Do not confuse valves in the heart with valves in veins: both prevent backflow, but they are in different places.
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