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Unlock This CourseYour heart is an amazing muscle that never stops working! It beats around 100,000 times every day, pumping blood to every part of your body. Think of it as your body's delivery service - it carries oxygen and nutrients to your cells and takes away waste products. Understanding how your heart works helps you appreciate why keeping it healthy is so important.
Key Definitions:
Your heart sits in your chest, slightly to the left of centre, between your lungs. It's about the size of your clenched fist and weighs roughly 300 grams. The heart is protected by your ribcage and surrounded by a special membrane called the pericardium.
The heart has four chambers that work together like a well-organised team. Think of it as a house with four rooms, each with a specific job to do.
The two upper chambers are called atria (singular: atrium). These are the 'receiving rooms' of the heart where blood enters.
Receives deoxygenated blood returning from the body through two large veins called the vena cavae. This blood is dark red because it's used up its oxygen.
Receives oxygenated blood from the lungs through four pulmonary veins. This blood is bright red because it's full of fresh oxygen.
The atria have thinner walls than ventricles because they only need to push blood down into the ventricles below, not pump it far.
The two lower chambers are called ventricles. These are the 'pumping rooms' that do the hard work of pushing blood out of the heart.
Pumps deoxygenated blood to the lungs through the pulmonary artery. It has moderately thick walls because it only needs to pump blood to the nearby lungs.
Pumps oxygenated blood to the entire body through the aorta. It has the thickest walls of all chambers because it needs to create enough pressure to push blood all around your body.
Your heart has four valves that act like one-way doors, making sure blood flows in the right direction and doesn't flow backwards. Imagine them as gates that open and close at exactly the right time.
Tricuspid valve: Between right atrium and right ventricle (has three flaps). Bicuspid valve: Between left atrium and left ventricle (has two flaps, also called mitral valve).
Pulmonary valve: Between right ventricle and pulmonary artery. Aortic valve: Between left ventricle and aorta. Both have three pocket-shaped flaps.
Your heart goes through a repeating cycle of contraction and relaxation. This happens automatically, about 70 times per minute when you're resting.
The atria contract, pushing blood down into the ventricles. The atrioventricular valves are open, but the semilunar valves are closed. This stage lasts about 0.1 seconds.
The ventricles contract powerfully, pushing blood out through the arteries. The atrioventricular valves slam shut (making the 'lub' sound) and the semilunar valves open. This stage lasts about 0.3 seconds.
The whole heart relaxes and fills with blood. The semilunar valves close (making the 'dub' sound) and the atrioventricular valves open. This stage lasts about 0.4 seconds.
Blood follows a specific pathway through your heart. It's like following a map through a building - there's only one correct route!
Here's the step-by-step journey blood takes through your heart:
1. Deoxygenated blood enters right atrium from body → 2. Blood flows through tricuspid valve into right ventricle → 3. Right ventricle contracts, pushing blood through pulmonary valve → 4. Blood travels through pulmonary artery to lungs for oxygen
5. Oxygenated blood returns from lungs to left atrium → 6. Blood flows through bicuspid valve into left ventricle → 7. Left ventricle contracts, pushing blood through aortic valve → 8. Blood travels through aorta to supply the whole body
Your heart rate changes depending on what you're doing. When you exercise, your heart beats faster to deliver more oxygen to your muscles. When you sleep, it slows down to conserve energy.
Your heart has its own built-in pacemaker called the sinoatrial node (SA node). This small group of cells in the right atrium sends out electrical signals that make your heart beat regularly, even when you're asleep!
Your nervous system can speed up or slow down your heart rate. The sympathetic nervous system increases heart rate during exercise or stress, while the parasympathetic nervous system slows it down when you're relaxed.
Professional athletes often have resting heart rates as low as 40-50 beats per minute, compared to the average 60-80 beats per minute. This is because their hearts have become more efficient through training - each beat pumps more blood, so fewer beats are needed. Their hearts are also larger and stronger, with thicker left ventricle walls that can pump more blood with each contraction.
Understanding how hearts can go wrong helps us appreciate why keeping them healthy is so important.
When arteries supplying the heart muscle become blocked with fatty deposits, reducing blood flow to the heart itself. This can cause chest pain and heart attacks.
When blood supply to part of the heart muscle is completely blocked, causing that part of the muscle to die. Quick medical treatment is essential.
When the heart beats irregularly - too fast, too slow, or with an abnormal rhythm. Some are harmless, but others can be dangerous.
Your heart works hard for you every day, so it's important to look after it! The good news is that many heart problems can be prevented through healthy lifestyle choices.
Regular exercise strengthens your heart muscle, improves circulation and helps maintain a healthy weight. Aim for at least 30 minutes of moderate exercise most days of the week.
A balanced diet with plenty of fruits, vegetables and whole grains helps keep your heart healthy. Limit saturated fats, salt and processed foods that can damage your cardiovascular system.