Human Heart

The human heart is a fist-sized, muscular organ that is hollow. Its job is to pump blood through the body's network of blood vessels. The heart, blood, and blood vessels are part of the circulatory system, which supplies all the body's cells with the oxygen and nutrients they need, and removes waste products. The heart has chambers, valves, arteries, and veins -- and a complex electrical system keeps everything working smoothly and makes the heart beat.

An Introduction to the Human Heart

In order to understand diseases that affect the human heart, it's important to know how the heart normally works. The human heart is a hollow, muscular organ about the size of a fist. Its job is to pump blood through a network of blood vessels. These vessels form a loop, which starts at the heart, goes out through your body, and then ends back at the heart again. Together, the heart, blood, and blood vessels are part of the circulatory system, which does two of the most important jobs in the body:
  • It carries oxygen and nutrients to all of your cells
  • It picks up carbon dioxide and other waste products that your body produces so they can be disposed of.

The Chambers of the Heart

The inside of a normal human heart is divided into four chambers:
  • The right atrium
  • The left atrium
  • The right ventricle
  • The left ventricle.

The Heart Valves

In a healthy human heart, there are valves that keep blood flowing in one direction. When they open, they only let the right amount of blood through, and then they close to prevent blood from flowing backward in between beats.
The circulatory loop begins with blood entering the right atrium of the heart. When the heart beats, blood flows from the right atrium into the right ventricle through a valve.
From the right ventricle, blood flows through another valve and then to the lungs, where it picks up oxygen. From the lungs, it flows back into the left atrium of the heart and through the mitral valve into the left ventricle. From the left ventricle, blood is pumped through the aortic valve and into the aorta, where it goes out to the rest of the body, bringing oxygen and nutrients to your cells.
For the human heart to work right, each of the four chambers must contract, or squeeze, at just the right time. Your heart has an electrical system that helps coordinate this timing.
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