REFERAT ENGLEZA: HEART

Publicat: 27 Iun 2008 00:00

Heart diseasNormal anathomy of the heartThe main heart diseasCausesTreathmentPrevention The function of the Heart Valves The heart consists of four chambers, two atria (upper chambers) and two ventricles (lower chambers). Blood passes through a valve before leaving each chamber of the heart. The valves prevent the backward flow of blood..Each valve has three flaps (leaflets), except the mitral valve, which only has two flaps. The four heart valves include the following:tricuspid valve - located between the right atrium and the right ventricle. pulmonary valve - located between the right ventricle and the pulmonary artery. mitral valve - located between the left atrium and the left ventricle. aortic valve - located between the left ventricle and the aorta. The heart`s electrical system functionAn electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node),). This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the heart`s chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart). The electrical impulse then travels from the sinus node to the atrioventricular (AV) node, where it stops for a very short period, and continues down the conduction pathways via the bundle of His into the ventricles. The bundle of His divides into right and left pathways to provide electrical stimulation to both ventricles. Normally, the electrical impulse moves through the heart`s conduction system, and the heart contracts. Each contraction represents one heartbeat. The atria contract a fraction of a second before the ventricles so the blood empties into the ventricles before the ventricles contract. Under some conditions, almost all heart tissue is capable of starting a heartbeat, or becoming the "pacemaker," just like the sinus node. An arrhythmia may occur when: the heart`s natural pacemaker (the sinus node) develops an abnormal rate or rhythm.the normal conduction pathway is interrupted.another part of the heart takes over as pacemaker. Heart attack and coronary heart disease A heart attack- (also known as a myocardial infarction) is the death of heart muscle from the sudden blockage of a coronary artery by a blood clot. Coronary arteries are blood vessels that supply the heart muscle with blood and oxygen. Blockage of a coronary artery deprives the heart muscle of blood and oxygen, causing injury to the heart muscle. Injury to the heart muscle causes chest pain and pressure. If blood flow is not restored within 20 to 40 minutes, irreversible death of the heart muscle will begin to occur. Muscle continues to die for 6-8 hours at which time the heart attack usually is "complete." The dead heart muscle is replaced by scar tissue. AtherosclerosisAtherosclerosis is a gradual process in which plaques (collections) of cholesterol are deposited in the walls of arteries. Cholesterol plaques cause hardening of the arterial walls and narrowing of the inner channel (lumen) of the artery. Arteries that are narrowed by atherosclerosis cannot deliver enough blood to maintain normal function of the parts of the body they supply. For example, atherosclerosis of the arteries in the legs causes reduced blood flow to the legs. Reduced blood flow to the legs can lead to pain in the legs while walking or exercising, leg ulcers, or a delay in the healing of wounds to the legs. Atherosclerosis of the arteries that furnish blood to the brain can lead to vascular dementia (mental deterioration due to gradual death of brain tissue over many years) or stroke (sudden death of brain tissue). CAUSES:High Blood Cholesterol (Hyperlipidemia) High Blood Pressure (Hypertension) Tobacco Use (Smoking)Diabetes (Diabetes Mellitus)Male Gender Family History of Heart Disease Treatment of heart attacks include:Anti-platelet medications to prevent formation of blood clots in the arteries. Anti-coagulant medications to prevent growth of blood clots in the arteries. Coronary angiography with either percutaneous transluminal coronary angioplasty (PTCA) with or without stenting to open blocked coronary arteries. Clot-dissolving medications to open blocked arteries Supplemental oxygen to increase the supply of oxygen to the heart`s muscle.Medications to decrease the need for oxygen by the heart`s muscle. Medications to prevent abnormal heart rhythms .

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