The structure of the heart
Laura Armstrong & Joe Wolfensohn
Teachers
Contents
Recall Questions
This topic requires prior knowledge of organisation and the structure and function of the lungs for gas exchange.
What is the main function of the lungs in the human body?
To carry out gas exchange by transferring oxygen into the blood and removing carbon dioxide.
What structures in the lungs are adapted for gas exchange?
The alveoli, which have a large surface area, thin walls, and a good blood supply.
What is an organ system?
A group of organs that work together to perform a particular function in the body.
Topic Explainer Video
Check out this @lauradoesbiology video that explains the structure of the heart, then read the study notes. Once you’ve gone through them, don’t forget to try the practice questions!
The Heart: Structure and Function
The heart is a muscular organ that pumps blood around the body through a double circulatory system.
Chambers of the Heart
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Right atrium – receives deoxygenated blood from the body via the vena cava.
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Right ventricle – pumps deoxygenated blood to the lungs via the pulmonary artery.
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Left atrium – receives oxygenated blood from the lungs via the pulmonary vein.
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Left ventricle – pumps oxygenated blood to the body via the aorta.
The left ventricle has a thicker muscular wall because it pumps blood to the entire body. The thicker muscular walls allow the left ventricle to contract with a greater force and generate a higher blood pressure.
Blood Vessels Associated with the Heart
|
Vessel |
Function |
|
Vena cava |
Brings deoxygenated blood from the body to the right atrium. |
|
Pulmonary artery |
Carries deoxygenated blood to the lungs. |
|
Pulmonary vein |
Brings oxygenated blood from the lungs to the left atrium. |
|
Aorta |
Carries oxygenated blood from the left ventricle to the body. |
|
Coronary arteries |
Supply the heart muscle itself with oxygenated blood. |
Diagram of the heart with chambers and blood vessels.
Valves in the heart and in the pulmonary artery and aorta prevent blood flowing the wrong way through the heart. They maintain a unidirectional flow of blood.
Heartbeat Regulation and Cardiac Output
Heartbeat Regulation
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The natural pacemaker is a group of cells in the wall of the right atrium.
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These cells generate electrical signals that control the heart rate.
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Artificial pacemakers are electrical devices used to regulate heart rhythm when the natural pacemaker fails.
What is Cardiac Output?
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Cardiac Output is the total volume of blood pumped by the heart per minute.
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It reflects the efficiency of the heart during rest or exercise.
Formula:
Cardiac Output (cm³/min )= Stroke Volume (cm³) × Heart Rate (bpm)
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Stroke volume = the amount of blood pumped out by one ventricle in one beat.
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Heart rate = number of beats per minute (bpm).
Example:
A person has a stroke volume of 75 cm³ and a heart rate of 80 bpm.
Cardiac Output = 75 × 80 = 6000 cm³/min
Key Terms
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Double circulation – Blood passes through the heart twice in one full circuit of the body. The right side of the heart pumps blood to the lungs. The left side of the heart pumps blood around the body.
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Pulmonary – To do with the lungs.
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Systemic – To do with the body.
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Pacemaker – A group of cells (or device) that regulates heart rate, found in the right atrium.
No answer provided.
Exam Tip
Be prepared to label heart diagrams and describe the direction of blood flow using named vessels.
You can remember that the vena cava is a vein as it begins with a V.
You can remember the Aorta is an artery as it begins with an A.
Then make sure to remember all arteries carry blood away from the heart and all veins carry blood in to the heart.
No answer provided.
Practice Question
Explain the difference between the right and left ventricle. (3 marks)
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The muscle wall of the left ventricle is thicker than the right.
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This increases the force of contraction and the pressure.
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To pump blood further around the body.
More Practice
Try to answer the practice question from the TikTok video on your own, then watch the video to see how well you did!