THE HEART

What is the heart?

The heart is the organ that supplies blood and oxygen to all parts of the body. It is about the size of a closed fist, weighs about 10.5 ounces and is shaped like a cone.

The heart is a muscular pump that provides the force necessary to circulate the blood to all the tissues in the body. Its function is vital because, to survive, the tissues need a continuous supply of oxygen and nutrients, and metabolic waste products have to be removed. Deprived of these necessities, cells soon undergo irreversible changes that lead to death. While blood is the transport medium, the heart is the organ that keeps the blood moving through the vessels. The normal adult heart pumps about 5 liters of blood every minute throughout life. If it loses its pumping effectiveness for even a few minutes, the individual's life is jeopardized.

The heart is located in the chest cavity just posterior to the breastbone, between the lungs and superior to the diaphragm. The heart is surrounded by a fluid filled sac called the pericardium. Blood is pumped away from the heart through arteries and returns to the heart through veins. The major artery of the body is the aorta and the major veins of the body are the vena cava.

How Does the Heart Work?

The heart is actually a muscle that works like a pump in distributing blood throughout the body. The heart has four chambers. The two at the top are the left and right atria and the two at the bottom are the left and right ventricles. Blood vessels lead in and out of these chambers.

Oxygenated blood from the lungs flows into your heart and is then pumped out to the rest of your body. Once the blood has delivered the oxygen to the tissues of the body, it returns to your heart and gets pumped back out to the lungs where it will be re-oxygenated.

How does blood flow through the heart?

Your heart muscle is a very efficient pump that delivers blood, oxygen and nutrients to your body.

The heart has four chambers - two on the right and two on the left. Both sides of the heart work together. The right side pumps blood into the lungs and the left side pumps blood into the organs and tissues of your body.

After your blood flows through the body, its life-giving oxygen and nutrients have been depleted. To replenish the oxygen and revitalize the blood, it must pass through the heart and then into the lungs again.

Right side: First the oxygen-depleted blood enters the heart through two large veins, the inferior and superior vena cava and then flows into the right atrium. From the right atrium, it passes through the tricuspid valve and then into the right ventrical. The blood is then pumped through the pulmonary valve and into the lungs.

Once in the lungs, carbon dioxide is removed and oxygen is added to the blood.

Left side: The pulmonary vein empties oxygen-rich blood, from the lungs, into the left atrium. From here, the blood flows from your into your left ventricle through the open mitral valve and finally, it is pumped through the aortic valve into the aorta - the blood vessel that feeds all of the other parts of your body.

When the ventricles are full, the mitral and tricuspid valves close. This prevents blood from flowing backward into the atria while the ventricles contract (squeeze) or "pump." This pattern is repeated continuously throughout your life, causing blood to flow continuously to the heart, lungs and other parts of the body.

How does the heart beat?

The atria and ventricles work together by alternately contracting (squeezing) and relaxing to pump blood through your heart. The heartbeat is triggered by electrical impulses that travel down a special pathway through your heart. The electrical system of your heart is the power source that makes this beating possible.

What and where are the coronary arteries?

The heart requires oxygen to function properly. But the blood that is pumping through the heart does not supply oxygen to the heart muscle itself. Special blood vessels attached to the outside of the heart, called coronary arteries, supply the heart with oxygen and nutrients needs. Three major arteries and a number of smaller vessels are designed to perform this function.