| |
Unique Home Furniture, Home Decorating and Home Decoration Store
Pulmonary Disease Now: But it is well established that chronic pulmonary disease now constitutes the largest single medical problem in the industrialized and highly polluted areas of northern Europe and is becoming increasingly frequent in the industrial cities of the U.S. Because the incidence of this disease increases with the time of exposure and the concentration of pollutants, we may expect, in fact, that the worst effects of air pollution will not be experienced until the end of this century.
Just as generalized, or systemic, hypertension can in time cause enlargement and failure of the left ventricle, pulmonary hypertension can cause enlargement and failure of the right ventricle. Pulmonary hypertension is most commonly caused by congestion in the lung circulation due either to the back pressure of a failing left ventricle or to mitral valve stenosis. A somewhat less common cause of pulmonary hypertension is an obstruction in the pulmonary circulation that has nothing to do with the left ventricle.
The valve that separates the right ventricle from the pulmonary artery is called the pulmonary valve. It opens during systole, to allow the blood to be pumped toward the lungs, and it closes in diastole to keep the blood from leaking back into the heart from the pulmonary artery. The pulmonary valve has three cusps, each one resembling a crescent, and it is known as a semi-lunar valve. The pulmonary valve does not need any cords to keep the cusps in place, but the tricuspid valve does. These cords are called chordae tendineae, and they are attached to the papillary muscle, a muscular outgrowth inside the right ventricle.
|
|
|
 |
Child-Education-Usa.com |
|
 |
 |
|
Menu |
|
|
| |
| |
|
|
| |
|
