Anatomy And Physiology
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How the Heart Works



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"How the Heart Works"
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The human heart pumps blood out to all parts of the body. You could say it is the engine of the body. Without it, there would be no blood circulating. The beating of the heart is heart muscle contracting and relaxing to send fresh supplies of oxygenated blood to all parts of the body to keep it performing its miracles through out a lifetime. Tiny little electrical nodes, the SA and AV nodes (sinoatrial and atria ventricular) begin the electrical current that keeps the blood flowing. The mighty little fist-sized organ, the heart, is the body's pump that pushes oxygenated blood to the rest of the body. When the heart is diseased and not up to its normal capacity, the body suffers.

The route the blood travels after being depleted of its oxygen and carrying waste in the form of carbon dioxide is through two large veins the inferior and the superior vena cava. From there it enters the right atrium. The tricuspid valve - three-flapped valve - opens to allow blood to the right ventricle. Then it is into the pulmonary circuit to pick up a new load of oxygen and nutrients and then by way of the pulmonary veins it returns to the left atrium. From there through the valve to the left ventricle it is again forced out into the aorta with its new refreshed blood on its way again.

The heart itself with all the hard work it does must have its own outlet of arteries and veins supplying the muscles - myocardium - with fresh oxygen and nutrients. Coronary vessels are separated into two branches, one supplying the right side of the heart and the other supplying the left side of the heart. Blocked arteries better known as myocardial infarctions - heart attacks - occur in these vessels.

We see pictures of the heart as a perfectly proportioned organs but its shape varies somewhat according to the size of its four chambers, which are not quite equally proportioned. As an example, the two upper chambers of the heart, which essentially are receivers of blood, are smaller than the two lower chambers of the heart, which send out blood. Therefore, the largest of the four chambers is the left ventricle. Its purpose is to eject blood forcefully through the pulmonary valve into the aorta to begin it coursing throughout the body. Half an inch thick muscles designed for heavy duty contractions make circulation possible and is, essentially, the primary work of the heart.

The atria or upper chambers are correspondingly smaller since they are lower in both volume and pressure. Septums, or flap closures, separate the chambers and keeps blood from back flowing. The pressure of the blood as regulated by the electric current allows the valves to open and close and is what gives the heart its beat. The purpose of all this activity is to pump blood with its nourishing supplies throughout the body. A new supply of oxygen is delivered via the arteries that branch into a tree like structure that finalize their mission by saturating all the tissues with new life giving properties of oxygen and nutrients.

The two blood highways, to and from the heart with their two tree-like structures meet when the tiniest branches of the arteries and veins evolve into capillaries. These are everywhere and no tissue is without its minute passage ways. The capillary walls are thin and gases, oxygen and carbon dioxide, pass easily through them by means of osmosis. In this amazing system, there is no intermingling of fresh and used blood and the circuits are each to their own. It is almost like night and night, one shading gradually into the other.

Regardless of what you have been taught, the heart has little to with the emotion of love. The organ responsible for this wonderful feeling is the brain. This misappropriation of facts probably originated in earlier times when less was known about how the body works. Although, it is true, once the brain gives the signal, the heart needs to pump the blood to where love can be nurtured and appreciated. Whatever, the heart is rightfully more attractive as the symbolic icon of love, especially with lovers, and anyway, how can we deny cupid?



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