Blood Components Diagram IGCSE Biology 0610

Blood Components Diagram: Cells, Plasma and Platelets

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Key diagram

Blood consists of plasma (the liquid), red blood cells (carry oxygen), white blood cells (fight infection by phagocytosis and antibody production), and platelets (involved in clotting).

The blood components diagram is tested as a labelling task and as structured questions linking each component to its function. Students must be able to draw and identify the four components and describe the roles of phagocytes and lymphocytes.

Drawing the four components

Draw a test tube or a magnified view of blood. The background liquid is plasma: a pale yellow fluid. Within it, draw: (1) many small biconcave discs without nuclei for red blood cells; (2) larger cells with visible nuclei for white blood cells; (3) tiny cell fragments for platelets.

White blood cells are much less numerous than red blood cells, so draw fewer of them. Show two types of white blood cell: a phagocyte with a lobed nucleus, and a lymphocyte with a large round nucleus.

Functions of each component

Plasma transports dissolved substances including carbon dioxide, urea, hormones, antibodies, nutrients (glucose, amino acids) and heat. Red blood cells contain haemoglobin, which binds oxygen in the lungs to form oxyhaemoglobin and releases it in the tissues. White blood cells defend against pathogens: phagocytes engulf and digest pathogens (phagocytosis), while lymphocytes produce antibodies. Platelets are cell fragments that release chemicals at a wound site, triggering the clotting cascade to form a fibrin mesh and prevent blood loss and pathogen entry.

Red blood cell adaptations revisited

Red blood cells have no nucleus (more space for haemoglobin), a biconcave disc shape (large surface area to volume ratio), and are small and flexible (can squeeze through capillaries). These features maximise oxygen transport.

Label checklist

Check these labels are present and correctly positioned before finishing your drawing.

✓ Plasma
✓ Red blood cells
✓ White blood cells: phagocyte
✓ White blood cells: lymphocyte
✓ Platelets
✓ Haemoglobin (inside red blood cells)

Try a diagram question (4 marks)

Describe the role of white blood cells in defending the body against disease. [4]

Show the answer and marking guidance

Phagocytes engulf and digest pathogens by phagocytosis.
Lymphocytes recognise antigens on the surface of pathogens.
Lymphocytes produce antibodies specific to those antigens.
Antibodies cause pathogens to clump together or mark them for destruction.

Original Cambridge-style practice written for this site.

Common diagram mistakes

Check these against your own drawing before moving on.

Drawing red blood cells with a nucleus.
Confusing platelets with white blood cells: platelets are cell fragments, not cells.
Stating that red blood cells carry carbon dioxide: it is mainly carried dissolved in plasma.
Forgetting that lymphocytes produce antibodies and phagocytes engulf pathogens (mixing up the two).