Your Heart and How It Pumps

Your heart is a fist sized pump that beats around 100,000 times a day without you ever thinking about it. Once you see how it works, a lot of what doctors check, and why, starts to make sense.

The body is built in levels, and organs are teams of tissues doing one big job. Now we meet the hardest working organ of them all. Your heart sits in the middle of your chest, tilted slightly to the left, and it has one job it never clocks off from: keeping blood moving. Every day it beats roughly 100,000 times and pushes around 5 litres of blood through your body, over and over, while you get on with your life. Let's open it up and look inside. You don't need to memorise the parts. Just follow the journey the blood takes. Four rooms and four doors Picture the heart as a house with four rooms. The two upper rooms are called the atria , and the two lower rooms are the ventricles . The upper rooms collect blood as it arrives. The lower rooms do the powerful pumping. A wall down the middle keeps the left side and the right side separate, because, as you'll see, they handle two different kinds of blood. Between the rooms are four valves , which work exactly like one way doors. They open to let blood through, then snap shut so it can't slip backwards. That snapping shut is, quite literally, the sound of your heartbeat. The familiar "lub dub" is the valves closing. The two loop journey Here's the part that makes everything click. Blood doesn't go round in one big circle. It does two loops, and the heart runs both at once. The first loop goes to the lungs . Blood that has already dropped off its oxygen around the body comes back tired and low on oxygen. It arrives in the right side of the heart, which pumps it the short distance to the lungs. There it picks up fresh oxygen and dumps the waste gas, carbon dioxide, which you then breathe out. The second loop goes to the body . That freshly oxygenated blood returns to the left side of the heart, which is the stronger side, because it has the big job. It pumps oxygen rich blood all the way out to your brain, your muscles, your toes, every cell that depends on it. Then the blood comes back, and the whole thing begins again. So the right side serves the lungs, and the left side serves the body. That single fact explains a surprising amount of heart medicine later on. The pipes: arteries and veins The heart doesn't work alone. It's the pump at the centre of a vast network of tubes called blood vessels, and together they make up your circulatory system . The vessels carrying blood away from the heart are arteries . The ones bringing it back are veins . Between them sit tiny vessels called capillaries, so narrow that blood cells pass through in single file. That's where the real handover happens: oxygen and food out to the cells, waste collected for disposal. The spark that sets the pace One last thing. What tells the heart when to beat? It has its own built in electrical system. A small patch of cells near the top, sometimes called the heart's natural pacemaker, sends out a steady electrical signal. That signal sweeps across the muscle and makes it squeeze in the right order, top rooms first, then the powerful lower rooms. This is why your heart can speed up when you run and settle when you rest, without you ever deciding it. Put it all together and you have a tireless two sided pump, with one way doors, its own electrical spark, feeding a network of pipes that reaches every corner of you. Remarkable, and running right now as you read this. What a doctor checks when examining your heart A doctor cannot see the heart directly. Instead, they build a picture of how well it is pumping using four simple methods. Looking. Before touching you, a doctor looks for visible clues. Swelling around the ankles can mean fluid is backing up because the pump is struggling. A bluish tinge to the lips, called cyanosis, suggests the blood is not carrying enough oxygen. Bulging neck veins can mean blood is not returning to the heart as freely as it should. Feeling. A doctor feels your pulse at the wrist, checking its rate, rhythm and character. They may also feel gently on your chest for the apex beat, the point where the heartbeat feels strongest. This gives a rough sense of the heart's size and position. Listening. Using a stethoscope, a doctor listens to the valves opening and closing: the "lub dub" you learned about above. An extra or unusual sound, a murmur, tells them blood may be moving in a slightly turbulent way, and prompts a closer look. Special tests. Blood pressure measurement shows how hard the left side is working to push blood around the body. Checking capillary refill shows how quickly colour returns to a fingertip after light pressure. Checking the pulses in the feet shows how well blood is reaching the furthest parts of the body. Together, these checks let a doctor judge whether the heart and its blood vessels are under strain, often long before any disease has a name. When this system is affected When the heart is not pumping as well as it should, people may notice symptoms such as breathlessness, tiredness, or swollen ankles. Other symptoms include a racing or fluttering feeling in the chest, dizziness, and chest discomfort. These symptoms are explored further in the lessons "Feeling Short of Breath", "Chest Pain: What Could It Be?" and "Palpitations: When Your Heart Feels Different".

The heart is a two sided pump, driven by its own electrical signal, sending blood to the lungs on one side and around the body on the stronger side.