From the moment heart begins beating until the moment it stops, the human heart works tirelessly. In an average lifetime, the heart beats more than two and a half billion times, without ever pursuing to rest. Like a pumping machine, the heart provides the power needed for life. This life-sustaining power has, throughout time, caused an air of mystery to surround the heart. Modern technology has removed much of the mystery, but there is still an air of fascination and curiosity.
A human being’s heart is about the size of that human being’s fist. As the body develops, the heart grows at the same rate as the fist. So an infant’s heart and fist are about the same size at birth.
The heart weighs between 7 and 15 ounces (200 to 425 grams) and is a little larger than the size of your fist. By the end of a long life, a person’s heart may have beaten (expanded and contracted) more than 3.5 billion times. In fact, each day, the average heart beats 100,000 times, pumping about 2,000 gallons (7571 liters) of blood.
The heart is located between your lungs in the middle of your chest, behind and slightly to the left of your breastbone (sternum). A double-layered membrane called the pericardium surrounds your heart like a sac. The outer layer of the pericardium surrounds the roots of your heart’s major blood vessels and is attached by ligaments to your spinal column, diaphragm, and other parts of your body. The inner layer of the pericardium is attached to the heart muscle. A coating of fluid separates the two layers of membrane, letting the heart move as it beats, yet still be attached to your body.
The heart has 4 chambers. The upper chambers are called the left and right atria, and the lower chambers are called the left and right ventricles. A wall of muscle called the septum separates the left and right atria and the left and right ventricles. The left ventricle is the largest and strongest chamber in your heart. The left ventricle’s chamber walls are only about a half-inch thick, but they have enough force to push blood through the aortic valve and into your body.
Amazing Heart Facts
Your heart is about the same size as your fist. As the body develops, the heart grows. An average adult body contains about five liters of blood. All the blood vessels in the body joined end to end would stretch 62,000 miles or two and half times around the earth. The heart circulates the body’s blood supply about 1,000 times each day.
Myocardium – Heart Muscle
The muscle responsible for pumping the blood is called the myocardium (myo means ‘muscle’, cardia means ‘heart’). The heart has three layers of tissue, the myocardium, the epicardium and the endocardium. The myocardium is the thick layer of Heart muscle made up predominantly of cells called myocytes. Its outside surface is covered by a thin glossy membrane, the endocardium covers the inside surface of your Heart’s four chambers, the valves and the muscles that attach to those valves.
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