Heart

Heart

Structure of the Heart

The human heart is a pear-shaped structure about the size of a fist. It lies obliquely within the chest cavity just left of centre, with the apex pointing downward. The heart is constructed of a special kind of muscle called myocardium, and is enclosed in a double-layered, membranous sac known as the pericardium(Verrier, Mittleman 1996 pp.289-307).

A wall of muscle divides the heart into two cavities: the left cavity pumps blood throughout the body, while the right cavity pumps blood only through the lungs. Each cavity is in turn divided into two chambers, the upper ones called atria, the lower ones ventricles.

Functions of the Heart

Blood flows through the heart in one direction only. It is prevented from backing up by a series of valves at various openings: the tricuspid valve between the right atrium and right ventricle; the bicuspid, or mitral, valve between the left atrium and left ventricle; and the semilunar valves in the aorta and the pulmonary artery. Each heartbeat, or cardiac cycle, is divided into two phases. In the first phase, a short period of ventricular contraction known as the systole, the tricuspid and mitral valves snap shut, producing the familiar "lub" sound heard in the physician's stethoscope(Gorman, Sloan 2000, pp.77-83).

Reason for Heart Attack

Blockage of arteries

Coronary Heart disease is a disease where the coronary arteries that supply blood to the heart become blocked. The blockage is in the form of a blood clot that can block a percentage of all five arteries (Flack et al. 1995. pp.592-600). Coronary arteries already narrowed by arteriosclerosis are made susceptible to blockage by a clot (coronary thrombosis), causing the death of the heart muscle supplied by the affected artery, a life-threatening event called a myocardial infarction, or heart attack.

Smoking and over weight

Some studies indicate that smoking doubles someone s chance of having heart disease. Unfortunately, many Americans do not follow healthy lifestyles. Over 33% of Americans are considered obese. This obesity leads to high cholesterol, increased blood pressure, and can even cause diabetes. As a society is seems that Americans have decided to live the way they want and to hell with what is good for us(Kessler et al. 1994. pp.8-19 ).

High Blood Pressure (Hyper tension)

Hypertension or high blood pressure, elevated blood pressure resulting from an increase in the amount of blood pumped by the heart or from increased resistance to the flow of blood through the small arterial blood vessels (arterioles). Hypertension is generally defined as a blood pressure reading greater than 140 over 90. When the cause is unknown, the condition is called primary, or essential, hypertension. When a cause can be identified (e.g., a disorder of the adrenal glands, kidneys, or arteries), the condition is known as secondary hypertension(Gorman, Sloan 2000, pp.77-83). Factors such as heredity, obesity, smoking, and emotional stress are thought to play a role; the usual immediate cause is an imbalance in the body's vasoconstriction/fluid retention systems, often involving a decrease in the kidney's secretion of the regulatory hormone, ...