The cardiovascular system is an elaborate network that performs 2 major tasks. Firstly it delivers oxygen and nutrients to body organs, and secondly it removes waste products of metabolism from tissue cells.
             The heart's major components 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 chambers walls are made up of a 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)
             Blood returning from the body through the venous system enters the heart through the right atrium, where it collects and is then pumped to the right ventricle. Each time the right ventricle contracts, it propels the blood, which is low in oxygen content into the lungs where it is enriched with oxygen. Pulmonary veins return the blood to the left atrium, which then contract and send it to the left ventricle. The left ventricle, the heart's main pumping chamber, ejects the blood through the aorta into the major circulatory network. Because it delivers blood to the entire body, this ventricle works much harder than any of the other chambers of the heart. As a result its walls can be more than half an inch thick which can be two or three times thicker than the right ventricle.
             Blood in the h...