What are the components of blood, and what causes cardiovascular disease?
The components of blood and their functions, the risk factors and development of cardiovascular disease, and ways of preventing and treating it.
A focused answer to the WJEC GCSE Biology section 1.4 topic on blood and cardiovascular disease, covering the components of blood (red cells, white cells, platelets and plasma) and their functions, the risk factors and development of coronary heart disease, and ways of preventing and treating it.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What this dot point is asking
WJEC wants you to name the four components of blood and their functions, explain how cardiovascular disease develops and its risk factors, and describe ways to prevent and treat it.
The components of blood
Blood is a tissue made of four main parts.
- Red blood cells: carry oxygen from the lungs to the body. They are packed with haemoglobin, which binds oxygen. They are biconcave (giving a large surface area) and have no nucleus (leaving more room for haemoglobin).
- White blood cells: part of the immune system. Some engulf and digest pathogens (phagocytes), and some produce antibodies (lymphocytes). They do have a nucleus.
- Platelets: small fragments that help the blood clot at a wound, forming a scab that stops bleeding and keeps out pathogens.
- Plasma: the pale yellow liquid part of blood. It transports the blood cells, dissolved nutrients (such as glucose and amino acids), hormones, antibodies, carbon dioxide and the waste urea.
How cardiovascular disease develops
The heart muscle is supplied with oxygen and glucose by the coronary arteries. In cardiovascular disease (such as coronary heart disease), fatty deposits build up inside these arteries, narrowing them. This narrowing is called atherosclerosis.
As the coronary arteries narrow:
- less blood, and so less oxygen and glucose, reaches the heart muscle,
- the heart muscle cannot respire as much, so it may not work properly,
- if an artery becomes completely blocked, part of the heart muscle is starved of oxygen and dies, causing a heart attack.
Risk factors
Several factors increase the risk of cardiovascular disease:
- a diet high in saturated fat (increases fatty deposits),
- smoking (damages the artery walls and reduces oxygen in the blood),
- lack of exercise,
- being overweight,
- high blood pressure,
- genetic factors inherited from parents.
Many of these are lifestyle factors that a person can change, while genetics cannot be changed.
Preventing and treating cardiovascular disease
Risk can be lowered by a healthier lifestyle: eating less saturated fat, not smoking, exercising regularly and keeping a healthy weight. Medical treatments include:
- Statins: drugs that reduce the amount of fatty deposit forming in the arteries.
- Stents: small mesh tubes inserted to hold a narrowed artery open so blood can flow.
- Surgery: for example a coronary bypass, using a vessel from elsewhere to carry blood around a blocked section.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC style4 marksDescribe how a red blood cell is adapted to carry oxygen.Show worked answer →
A 4-mark question linking structure to function.
A red blood cell is full of the red pigment haemoglobin, which binds to oxygen to carry it. It has a biconcave disc shape, which gives a large surface area for oxygen to diffuse in and out quickly. It has no nucleus, leaving more room for haemoglobin. It is small and flexible so it can squeeze through narrow capillaries.
Markers reward: contains haemoglobin to carry oxygen; biconcave shape for large surface area; no nucleus for more haemoglobin; small and flexible for capillaries. Saying "it is red" is not an adaptation.
WJEC style6 marksExplain how cardiovascular disease develops, and describe two ways a person can reduce their risk.Show worked answer →
A 6-mark extended question. Award marks for the development and for the prevention.
Cardiovascular disease develops when fatty deposits build up inside the coronary arteries, narrowing them (atherosclerosis). This reduces blood flow to the heart muscle, so less oxygen and glucose reach it. If a coronary artery becomes blocked, part of the heart muscle is starved of oxygen, causing a heart attack.
Risk can be reduced by eating less saturated fat (to reduce fatty deposits), not smoking, exercising regularly, keeping a healthy weight and reducing blood pressure.
A top answer explains the narrowing of the coronary arteries, the reduced oxygen supply to the heart, and gives at least two sensible lifestyle changes with reasons. Listing risk factors without explaining the narrowing of the arteries misses the development marks.
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Sources & how we know this
- WJEC GCSE Biology specification (from 2016) — WJEC (2016)