IGCSE Biology / Blood and circulation

Coronary arteries and heart disease revision notes

Edexcel International GCSE Biology (4BI1), chapter 5: Blood and circulation, specification point 2.67. Free lesson.

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Coronary arteries supply the heart muscle with oxygen and glucose. If fatty plaques narrow or block these arteries, they can cause angina or a heart attack.

How the coronary arteries feed the heart

The heart muscle contracts constantly, so it needs a constant supply of oxygen and glucose for respiration. Blood inside the heart chambers cannot supply the muscle because the heart wall is too thick for oxygen to diffuse through it. Instead, the coronary arteries bring blood to capillaries in the heart muscle. The two coronary arteries branch from the aorta, soon after it leaves the left ventricle. The left coronary artery runs across the front of the heart. The right coronary artery supplies the other side. The arteries branch into smaller vessels and then into capillaries,…

How a plaque can lead to angina

Coronary heart disease develops over years. Fatty deposits, mainly cholesterol, build up in the lining of a coronary artery. These deposits are called plaques. As a plaque grows, the artery narrows, so less blood, oxygen and glucose reach the heart muscle. With less oxygen and glucose, the muscle cannot respire aerobically enough during exertion. This can cause angina, which is pain caused by reduced blood flow to the heart muscle.

How a blockage causes a heart attack

The rough surface of a plaque can cause a blood clot to form. If the clot blocks the artery completely, the muscle beyond the blockage receives no oxygen, cannot respire and dies. This is a heart attack. Angina is pain from reduced blood flow. A heart attack is the death of heart muscle due to a complete blockage.

Risk factors and why they matter

A risk factor answer needs a reason: explain how the factor increases the chance of plaques forming or of the heart muscle receiving less oxygen. Some factors can be changed, while age and genetics cannot. Smoking: carbon monoxide reduces the oxygen the blood can carry, and nicotine raises blood pressure. A diet high in saturated fat: raises blood cholesterol, so plaques build up faster. High blood pressure: damages the artery lining, making plaques more likely to form there. Lack of exercise: can lead to higher blood pressure and obesity, both of which raise the risk.…

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