Heart & Blood Circulation

Children aged 9–11 move from 'the heart pumps blood' to the double-loop circulatory system: a four-chambered pump (two atria receive, two ventricles push) driving one loop to the lungs to pick up oxygen and one loop to the body to deliver it, through arteries (away from heart, high pressure), veins (back to heart, with valves) and capillaries (walls one cell thick, where exchange happens). Blood is a mixture — red cells (oxygen), white cells (fight infection), platelets (clotting) and plasma. Teach it as a JOURNEY a drop of blood takes, tracing the circuit repeatedly until the double loop and its purpose become obvious: blood reloads oxygen at the lungs, comes back to the heart to be pumped out again, and unloads oxygen at the body. Ground vessel types in things children can feel: the wrist/neck pulse is an artery; the blue-looking lines on the back of the hand are veins. A driveable flow model is the primary vehicle; anatomy-labelling, a 3D heart for orientation, and a consolidation quiz are complementary scaffolds.

• 'The heart makes blood' — it pumps blood, it does not manufacture it (blood cells are made in bone marrow).
• 'Blood is just red liquid' — missing that it is a mixture of cells, platelets and plasma, each with a job.
• 'Arteries are red and veins are blue' — vessels are not coloured; the shorthand refers to oxygen level, and deoxygenated blood is dark red, not blue. Veins only look blue through skin.
• 'Blood does one loop around the body' — missing the double circuit; children often think blood goes heart→body→heart and forget the separate lung trip to reload oxygen.
• 'The heart is on the left and heart-shaped' — it sits centrally behind the breastbone, tilted slightly left, and is a fist-sized muscular pump, not the symbolic shape.
• 'Capillaries are just tiny tubes' — missing that their one-cell-thick walls are the whole point: they are WHERE exchange happens.

• Double-loop circuit diagram (heart in the middle, lung loop on one side, body loop on the other) traced as a continuous path
• Four-chamber cutaway of the heart with arrows showing receive-then-push (atria fill, ventricles pump)
• Oxygen colour gradient — blood reddening at the lungs, darkening at the tissues — rather than fixed red/blue vessels
• 'Jar of blood' separation showing the four components layered (plasma, white cells/platelets, red cells)
• The pulse as a felt representation of the heartbeat driving blood through an artery

• Trace a single drop of blood around the WHOLE double loop, out loud and repeatedly: body → vein → right atrium → right ventricle → lungs (drop O2 low, reload) → left atrium → left ventricle → body → repeat. The double loop only makes sense as a continuous circuit, not a labelled diagram.
• Anchor vessel names to the body: find the pulse (an artery pushing), point out surface veins, and explain capillaries as the too-small-to-see meeting point where oxygen leaves and carbon dioxide is collected.
• Colour-code by oxygen, not by vessel: blood reddens as it passes the lungs and darkens as the body uses the oxygen — so students see WHY two loops exist, rather than memorising 'arteries red, veins blue' (a misleading shorthand).
• Separate the two ideas of 'what blood is made of' from 'where blood goes' — first build the four-part composition (red cells, white cells, platelets, plasma) with a jar-of-blood model, then set that mixture moving through the loop.
• Use the child's own body as the manipulative: measure resting pulse, then link a faster pump to needing more oxygen delivered — previewing the circulation+breathing integration topic.