The major components of the heart are a hollow muscular pump and a circulatory system of large and small elastic vessels that transport blood throughout the body.

The heart is the central organ of the cardiovascular system and it is located between the two lungs in the middle of the chest, although two-thirds of the heart lies to the left of the breastbone and one-third to the right. The adult heart is approximately the size of two clenched fists and it is shaped like a cone, weighing between 7 to 15 ounces depending on the size of the individual.

The human heart is divided into four chambers - the right atrium and the right ventricle and the left atrium and the left ventricle. The walls of the chambers are made up of myocardium muscle that contracts rhythmically under the stimulation of electric currents. A wall of muscle called the septum separates the left and right atria and the left and right ventricles from each other. (See Appendix 1a)

Systole is the phase during which blood is ejected from the ventricles and takes up the remaining third. During diastole, the sinus node generates an impulse that forces the two atria to contract. In this phase the tricuspid and mitral valves are open and the blood is propelled from the atria into the relaxed ventricles. By the end of diastole, the electric impulse reaches the ventricles, causing them to contract.

Below is a table to show the most common types of congenital heart disease and the type of defect that has occurred.

Some common words found in the essay are:
Arrhythmias Abnormalities, Endocarditus ABE, Pericarditis Infections, Rheumatic Fever, Systole Diastole, Normal Heart, Heart Circulation, Valves Blood, Physiology Seeley, Wrong Heart, heart disease, heart muscle, cardiac cycle, rheumatic fever, congenital heart, coronary artery, left ventricle, heart valves, infective endocarditis, left atrium, tricuspid mitral valves, congenital heart disease, low density lipoproteins, pulmonary artery aorta, bundle purkinje fibres,
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