11.2 Heart

2026 Syllabus Objectives

By the end of this subtopic, you should be able to:

  1. Identify the structures of the mammalian heart, including: the muscular wall, the septum, left and right ventricles and atria, atrioventricular and semilunar valves, and coronary arteries.
  2. Explain the relative thickness of the muscle walls of the left and right ventricles, and of the atria compared to the ventricles.
  3. Describe how the heart works — including the contraction of the atria and ventricles and the action of the valves during a heartbeat.
  4. State that blood is pumped away from the heart in arteries and returns to the heart in veins.
  5. State that heart activity can be monitored by ECG, pulse rate, and listening to valve sounds.
  6. Investigate and explain the effect of physical activity on heart rate.
  7. Describe coronary heart disease in terms of blocked coronary arteries and state its possible risk factors.
  8. Discuss the role of diet and exercise in reducing the risk of coronary heart disease.

Main Content

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1. Structures of the Mammalian Heart

The heart is a muscular pump located in your chest, slightly to the left. Its job is to pump blood around your entire body, non-stop, every day of your life. To do this effectively, it has several important structures.

The Four Chambers

The heart is divided into four hollow spaces called chambers. Think of them as four rooms inside the heart, each with a specific job.

  • Right Atrium — The upper-right chamber. It receives blood coming back to the heart from the body. This blood has already delivered its oxygen to the body's cells, so it is low in oxygen.
  • Right Ventricle — The lower-right chamber. It receives blood from the right atrium and pumps it to the lungs, where the blood picks up fresh oxygen.
  • Left Atrium — The upper-left chamber. It receives freshly oxygenated blood returning from the lungs.
  • Left Ventricle — The lower-left chamber. It receives blood from the left atrium and pumps it out to the entire body. This is the most powerful chamber in the heart.

🧠 Memory tip: "A" for Atria = upper chambers (they Arrive/receive blood). "V" for Ventricles = lower chambers (they pump blood out Via vessels).

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