Anatomy And Physiology

Heart Disease

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Diseases of the heart and cardiovascular system affect one in four people between the ages of thirty and sixty five. Risk factors include: Smoking, obesity, a high amount of blood cholesterol, a lack of physical exercise, high stress levels and poor diet.

One of the most frequent diseases occurring within the heart is a myocardial infarction, commonly known as a heart attack. This occurs when blood supply to the heart becomes obstructed causing damage to any given amount of tissue; the area of tissue affected may even die. The word infarct refers to the damaged tissue and it can occur in any part of the body, however, the most common place is within the heart's myocardium which is the middle layer of the heart wall.

Further tissue damage tends to occur when the blood supply is restored. This is because the damaged tissue releases an enzyme known as Xanthoxidase, which reacts with the oxygen from the fresh blood supply and converts into Superoxide Free Radicals. These cause colossal tissue damage, but the good news is that certain drugs such as Superoxide Dismutase can be administered to prevent the production of the free radicals and therefore, assist in keeping the tissue damage to a minimum.

Ischaemic heart disease occurs when one or more branches of the coronary arteries become narrowed. This can be due to a plaque build up within the artery walls which ultimately causes a blockage, or it can be complicated by thrombosis, commonly known as a blood clot, and this happens when the build up of plaque causes the arterial wall to rupture; this stimulates the platelets which are the clotting factor within the blood, and pieces of the clot can break off and travel within the arteries and eventually become lodged within the smaller blood vessels and therefore cause a blockage. Ischaemic heart disease can be chronic or acute. In chronic cases several small infarcts form and can lead to a weakness in the myocardium which can cause heart failure. In acute ischaemic heart disease, one or more of the large arteries become blocked and is usually complicated by thrombosis. The infarct covers a large area and disrupts various heart functions and death can suddenly occur.

Angina Pectoris causes severe pain upon physical exertion. In this condition the artery wall becomes viscous and inflexible. It generally allows normal blood flow during rest and moderate exercise but can not sufficiently dilate during strenuous exercise to allow for the increase in blood flow. Pain will diminish with the cessation of strenuous effort and/or with the ingestion of drugs such as vasodilators.

Diseases of the heart valves include stenosis and incompetence. Stenosis occurs when there is a narrowing of the valve opening and this can come about due to inflammation or a build up of materials at the edges of the valve cusps, causing them to adhere to each other. Stenosis can sometimes occur in conjunction with incompetence, although each condition can arise independent of each other. Incompetence occurs when the valve is unable to close; the blood can then flow back into the heart ventricle during relaxation.

Although a majority of these diseases are frequently brought on as a result of an unhealthy lifestyle, there are many occasions whereby diseases of the heart and cardiovascular system are unavoidable, for example, heart complications can arise as a result of shock, and of course, there may be hereditary factors. Heart disease can come about as a secondary complication arising from elsewhere in the body, for example, periocarditis and myocarditis which are in essence an inflammation within the heart wall. The pericardium is the outer layer and as we have seen, the myocardium is the middle layer. Inflammation within these areas can come about due to various bacterial infections within other parts of the body and/or as a result of a depressed immune system often following certain treatments such as chemotherapy and radiotherapy.

The diseases listed here are among the most common within the heart and cardiovascular system, however there are many more, and although heart and cardiovascular disease may not always be avoidable, as always, preventative intervention is better than cure.

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