Structure of the Heart: What Biology Students Need to Know

Biology students, are you ready to dive into the heart of the A Level course? 

Well you’ve come to the right place! This blog post draws from our NEW CIE A Level Biology Revision Notes, and is the perfect starting point for learning all about the human heart and circulatory system.

Whether you’re following the Edexcel, OCR, AQA or CIE course, you’ll need to understand both the structure of this crucial organ and how it functions to keep each one of us alive. 

Of course, if you’re an aspiring medical or biomedical student then this is a topic you’ll need to be super confident with, so don’t be tempted to skip over it. To help you get to grips with the content, we’ve included some of our brilliant bespoke diagrams. 

So bookmark this blog post and prepare to learn

The human heart

Our hearts are powerful muscles; did you know that the average heart will beat around 115,000 times and pump over 9,000 litres of blood around the body each day?

The constant circulation of blood allows oxygen and other essential solutes to be delivered straight to other organs and tissues, and facilitates the carrying away of waste products like carbon dioxide. 

The heart is located inside the chest cavity, slightly to the left of centre, and is protected by the pericardium (a tough, fibrous tissue sack). 

Because the basic beating of the heart is controlled by internally-generated electrical activity (it is myogenic), it could even beat outside of the body!

The structure of the heart

The heart has a very specialised structure so that it can carry out its function effectively. Here’s how the different parts work together in sequence: 

  1. Oxygenated blood from the lungs enters into the left atrium via the pulmonary vein 
  2. The left atrium contracts to force the blood into the left ventricle, where another contraction forces the blood through the aorta and around the body under high pressure 
  3. After having circulated the body, the deoxygenated blood returns to the right atrium of the heart at a lower pressure (via the vena cava)
  4. The blood is then moved through the right ventricle and pumped into the lungs (via the pulmonary artery) where is is reoxygenated 
  5. The cycle begins again 

Look at the diagram below to learn the names of each part of the heart (you’ll need to be able to label it from memory). 

Valves in the heart

Valves are like one-way gates that control the flow of blood inside the heart. They are essential to its functioning, and will only open if the pressure of blood behind them is greater than the pressure in front. 

  • The right atrium and right ventricle are separated by the atrioventricular valve, which is otherwise known as the tricuspid valve 
  • The right ventricle and the pulmonary artery are separated by the pulmonary valve 
  • The left atrium and left ventricle are separated by the mitral valve, which is otherwise known as the bicuspid valve 
  • The left ventricle and aorta are separated by the aortic valve

‘Leaky’ heart valves (when the valve fails to completely control the blood flow) can become a serious problem amongst older people, with symptoms including shortness of breath, fatigue and swelling. Treatments include medicines, surgical repair or surgical valve replacements.

You’ve made a great start, but don’t stop here!

Once you’ve learnt all of this information about the heart’s structure, you’ll be ready to tackle the remaining half of the topic content: how electrical activity and pressure changes drive the Cardiac Cycle. 

If you are a CIE student, you can find the complete set of Revision Notes here. 

Once you’ve finished revising the whole topic, head to the relevant Topic Questions for your exam board to put that new knowledge to the test.


Edexcel A Level Biology

Edexcel International A Level Biology

AQA A Level Biology

CIE A Level Biology (until 2021)

CIE A Level Biology (from 2022)

OCR A Level Biology

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