🔬 Scientific Overview
The heart is a muscular organ roughly the size of your fist. It works as the central pump of the circulatory system, sending blood throughout the body to supply oxygen and nutrients and remove carbon dioxide and waste.
🧬 Structure of the Heart
The heart has four chambers:
| Chamber | Role |
|---|---|
| Right atrium | Receives deoxygenated blood from the body via the vena cava. |
| Right ventricle | Pumps deoxygenated blood to the lungs via the pulmonary artery. |
| Left atrium | Receives oxygen-rich blood from the lungs via the pulmonary veins. |
| Left ventricle | Pumps oxygenated blood to the body through the aorta. |
Each chamber has valves that prevent backflow:
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Tricuspid valve (right atrium → right ventricle)
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Pulmonary valve (right ventricle → pulmonary artery)
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Mitral valve (left atrium → left ventricle)
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Aortic valve (left ventricle → aorta)
🌀 How Blood Circulates – Step by Step
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Deoxygenated blood enters the right atrium from the body.
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It moves to the right ventricle, which pumps it to the lungs for oxygenation.
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Oxygen-rich blood returns to the left atrium.
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It flows into the left ventricle, which pumps it to the entire body via the aorta.
🫀 This cycle is repeated about 100,000 times per day!
⚙️ Heartbeat and Electrical System
The heart beats thanks to its own electrical system, which functions like a natural pacemaker:
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The sinoatrial (SA) node in the right atrium generates electrical impulses.
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These impulses spread across the atria, causing them to contract.
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The signal then moves to the atrioventricular (AV) node, then down the Bundle of His, and into the Purkinje fibers—causing the ventricles to contract.
⏱ A normal resting heart rate is about 60–100 beats per minute.
📊 Amazing Heart Facts
| Fact | Detail |
|---|---|
| ❤️ Beats per year | ~35 million times |
| 🩸 Pumps per day | ~7,500 liters (2,000 gallons) |
| 🧠 Heart-brain connection | Emotions influence heart rhythm via the vagus nerve |
| 🔋 Own electricity | The heart can beat outside the body (shortly) if oxygenated |
| 👶 Baby's heart | Starts beating ~day 22 after conception |
🏺 Interesting Historical Facts
| Period / Person | Historical Note |
|---|---|
| Ancient Egypt | Believed heart was the seat of intelligence; preserved it in mummies. |
| Hippocrates (c. 400 BCE) | Described heart as the source of heat. |
| Galen (2nd century CE) | Thought blood moved in a back-and-forth motion, not circulatory. |
| William Harvey (1628) | Revolutionized medicine by proving blood circulates in one direction via the heart – a landmark discovery. |
| First heart surgery | 1893, by Dr. Daniel Hale Williams, a Black American physician. |
| First successful heart transplant | 1967, by Dr. Christiaan Barnard in South Africa. |
💡 Bonus: Fun Trivia
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A blue whale's heart weighs over 150 kg (330 lbs) and is the size of a golf cart.
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Your heart can sense stress, love, fear, and even adjusts its rhythm based on emotional state.
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Laughing is good for the heart: it boosts blood flow by ~20%.
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The heart has its own immune cells to defend against damage.