Blood and blood vessels — Edexcel GCSE Biology
How red blood cells, white blood cells, plasma, platelets and the three types of blood vessel are suited to their jobs.
Revision notes
2 short notes, in the order of the specification. Each one in short:
Blood is a tissue made of plasma with red blood cells, white blood cells and platelets suspended in it. Red blood cells are biconcave discs with no nucleus, full of haemoglobin, which binds to oxygen. Phagocytes engulf pathogens and lymphocytes make antibodies. Plasma carries dissolved substances, and platelets help the blood clot at a wound.
There are three types of blood vessel. Arteries carry blood away from the heart at high pressure and have thick, muscular walls with elastic fibres. Veins carry blood back to the heart at low pressure, with a wide lumen and valves to stop backflow. Capillaries have walls one cell thick, giving a short diffusion distance for exchange.
Exam questions
7 exam-style questions (18 marks), each with its mark scheme.
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12 cards: flip them, mark what you knew, and practise the rest.
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The whole of exchange and transport in animals on one page, so you can see where this subtopic fits.
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Quick check questions
Which part of the blood carries oxygen, and what is the name of the substance that binds to it?
Show answer
Red blood cells; haemoglobin.
What is the job of phagocytes?
Show answer
They engulf and digest pathogens.
Which blood vessels have valves?
Show answer
Veins.
Why are capillary walls only one cell thick?
Show answer
To give a short diffusion distance for exchange of substances.
Frequently asked questions
How are red blood cells adapted to carry oxygen?
Red blood cells have a biconcave disc shape, which gives a large surface area for absorbing oxygen. They are full of haemoglobin, which binds to oxygen to form oxyhaemoglobin, so each cell can carry a lot of oxygen. They have no nucleus, which leaves more room for haemoglobin. Their job is to carry oxygen.
How do white blood cells fight infection?
There are two types of white blood cell. Phagocytes are flexible, so they can change shape to surround pathogens, engulf them and digest them, which is called phagocytosis. Lymphocytes make and release antibodies into the blood. The antibodies attach to specific pathogens and help to destroy them.
Why do arteries have thick elastic walls?
Arteries have thick, muscular walls with elastic fibres because they carry blood away from the heart at high pressure. The thick wall can stand the high pressure, and the elastic fibres let it stretch and spring back with each heartbeat. Arteries also have a narrow lumen and, unlike veins, no valves.
Why do veins have valves but arteries do not?
Veins have valves because they carry blood back to the heart at low pressure, and the valves stop the blood flowing backwards. Veins also have a thinner wall and a wide lumen, which lets blood flow easily. Arteries carry blood away from the heart at high pressure, and they have no valves.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026