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Blocked arteries and circulatory health

Explain how plaque and clots can interrupt blood supply, distinguish heart attacks from strokes caused by blockage, and connect diet, activity and smoking to risk.

  • SEC G1 Science 2027

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Why does the location of a blockage matter?

Blood supplies body cells with oxygen and digested food substances. A blockage can interrupt that supply. To explain the damage, name the affected tissue and trace what can no longer reach it.

Plaque can narrow an artery

Plaque is a build-up of fatty material and other substances in an artery wall. It can grow inward, narrowing the lumen, the space blood flows through. This can restrict the supply of blood to tissues. Fat from a meal does not simply pour into an artery and plug it immediately.

An area of plaque can break open, allowing a blood clot to form on it. A clot can block the remaining space. This is different from the useful clotting that reduces blood loss at a cut: the effect depends on where the clot forms.

Plaque, clotting and blocked blood supplyThree schematic artery cross-sections show an open lumen, plaque growing inward from the wall and narrowing the lumen, and a clot blocking the remaining lumen beside plaque. Two conditional labels distinguish blocked supply to heart muscle from blocked supply to part of the brain.Open arteryLumenArtery wallBlood can passNo plaque shownPlaque build-upPlaqueLumenLess space for bloodFlow may be restrictedClot blocks arteryPlaqueClotBlood cannot passThrough-flow is blockedWhere the supply is blocked matters.Blocked supply to heart muscleCan cause a heart attackBlocked supply to part of the brainCan cause a stroke
Scroll diagram horizontally to read all labels.
The lumen is the space blood flows through. Plaque can narrow it; a clot can block it. These are possible states, not an inevitable sequence. The drawings are not to scale and do not represent measured blood flow. This diagram shows stroke caused by a blockage; other strokes involve bleeding.

Heart attack and stroke

If blood supply to heart muscle is severely reduced or blocked, that muscle may be damaged or die. This can cause a heart attack. The heart muscle needs its own blood supply; blood inside a heart chamber is not a substitute for blood reaching its cells.

If supply to part of the brain is blocked, brain cells can be damaged or die. This can cause a stroke. The blockage mechanism is the one studied here. Some strokes instead result from bleeding in or around the brain, so “stroke” does not always mean an artery is blocked.

Read the NHLBI explanation of plaque and heart attacks and the Newcastle Hospitals explanation of stroke types for more detail.

Habits affect risk

A risk factor makes an outcome more likely; it does not guarantee that outcome. Diet, physical activity and smoking can affect the risk of heart disease, high blood pressure and stroke.

  • Diet: a balanced diet supports health. Frequently eating too much saturated fat can contribute to unhealthy blood cholesterol levels and plaque build-up. Too much salt can contribute to high blood pressure in people who are sensitive to it.
  • Physical activity: regular suitable activity supports circulatory health and can help lower the risk of high blood pressure. Being active does not guarantee protection from disease.
  • Smoking: tobacco smoke damages blood vessels and raises the risk of circulatory disease. Avoiding smoking removes this harmful exposure.

High blood pressure can also raise the risk of heart disease and stroke. Changing habits can lower risk; it does not guarantee that existing plaque or disease disappears. The NHLBI guide to high blood pressure explains these risk factors.

Worked examples

Modelled example 1

From a blocked artery to damaged heart muscle

Core

Problem

Plaque in an artery supplying heart muscle breaks open and a clot blocks the remaining lumen. Explain how this can lead to a heart attack.

Study the worked solution

  1. Trace supply to the affected tissue

    Method

    Link the blockage to what the heart muscle cells no longer receive.

    Reason

    The outcome depends on the tissue supplied by the artery, not simply on the presence of plaque somewhere in the body.

    Working

    1. The clot blocks blood flow through the artery to part of the heart muscle.
    2. Those cells receive too little oxygen and nutrients to support their normal activity.
    3. If the supply is not restored promptly, cells can be damaged or die. This damage can cause a heart attack.

Common misconception 2

Clotting depends on location

Find and correct the mistake

Learner response

“Blood clots are always harmful, so platelets should never help blood clot.” Correct the claim using a cut and a clot inside an artery.

Compare the two locations

View solution step by step

  1. Compare loss of blood with loss of supply

    Method

    Explain the different jobs or effects of the two clots.

    Reason

    A clot can seal damage at a cut, but it can also obstruct blood flowing to tissues.

    Working

    At a cut, platelets help blood clot and reduce blood loss. A clot inside an artery can instead block its lumen and interrupt the supply to tissues beyond it. The harm depends on where the clot forms and what blood supply it affects; clotting is not always harmful.

Challenge 3

Build a complete cardiovascular risk chain

Minimal support

Problem

A person smokes, is usually inactive and often eats foods high in saturated fat. Explain how changing these habits could reduce cardiovascular risk. Your answer must connect lifestyle, plaque or vessel narrowing, blood flow and a possible outcome.

Write a linked chain, not a list

Hints

Hint 1: middle link

How does plaque affect the space available for blood flow?

Hint 2: outcome

What can happen if blood supply to heart muscle or part of the brain is blocked?

View solution step by step

  1. Connect habit to consequence

    Method

    Explain why reducing smoking, improving diet and becoming active can lower risk.

    Reason

    These changes can reduce factors that promote vessel damage and plaque build-up while supporting circulatory health.

    Working

    Avoiding smoking, choosing a balanced diet lower in saturated fat and increasing suitable activity can reduce cardiovascular risk. Less plaque build-up means arteries are less narrowed, so blood is less likely to be restricted or blocked. This lowers the risk of a heart attack if heart-muscle supply is blocked, or a stroke if brain supply is blocked.

Practise independently

A clot blocks an artery supplying part of the brain. A learner calls this a heart attack because “all arteries come from the heart”. Correct the explanation using the affected tissue, its blood supply and the possible damage.

Check your answer

The affected tissue is part of the brain, so this blockage can cause a stroke. Reduced blood supply deprives those cells of oxygen and nutrients and can damage them. A heart attack involves damage to heart muscle, not damage to brain tissue simply because the blood originally came from the heart.

One-minute check

Without looking back, explain plaque → narrowing or clot → reduced blood supply → tissue damage. Then contrast a heart attack with a stroke caused by blockage, and explain why a risk factor is not a guarantee.

Syllabus and review details

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