The Human Heart

The heart is one of the most important organs in your body. So what does it do? It's function is to pump blood to all the other organs. But the heart can not function alone, it has other organs and blood vessels helping it. The human heart is a pear shaped and about the size of a human fist. It is made of muscle and there are three different layers. The outer layer is called the epicardium. The middle layer is called the myocardium which is made of muscles that contract. The inner layer is called the endocardium, this layer is in contact with the blood. The heart is divided into four chambers. The left side and the right side, which is then divided into atriums and ventricles. The atriums are the top chambers and the ventricles are the bottom chambers. The right side pumps blue blood (deoxygenated) while the left side pumps red blood. (oxygenated) The blood in the heart flows in one direction at a constant rate which means none of the chambers get overfilled. But what happens when we start running and needing more blood? The heart still goes at a constant rate but only faster.The normal rate for an adult is 72 beats per minute. Then for the blood from flowing backward, there are tricuspid, bicuspid, aortic, and pulmonary valves. The blood goes from the atriums to the ventricles this is never changed or swapped around. Blue blood first enters the heart from either the inferior vena cava or the superior vena cava. The blood doesn't come randomly from either one of these veins. All the deoxygented blood from parts of the body above the heart, comes in throught the superior vena cava into the left atrium. Then all the deoxygenated blood from parts of the body below the heart, comes from the inferior vena cava into the heart. Once there, it is pumped into the right ventricle through a flap called the tricuspid valve. From the right ventricle it goes through the pulmonary valve into the pulmonary artery. From there it goes to the lungs where it becomes oxygenated