Page 16, History of Cardiovascular Physiology, Dr. D. Penney


Misconceptions (Continued....):

Textbooks sometimes contain errors, so don't believe everything you read. Think about what is written and ask questions. For example, an older edition of the well known cardiology textbook by J. Willis Hurst, showed right and left atrial contraction occurring simultaneously, whereas, the right atium begins to contract a little before the left atrium because the primary pacemaker is located in the right atria.

Many texts give the mistaken impression that the heart does a major amount of work against gravity; for example, that the right ventricle has difficulty raising blood to the level of the top of the lung, this being the reason why the upper areas of the lung are usually less well perfused. Henry Badeer, in some very nice essays, demolished that idea.

Other texts state that the aortic valve closes when the pressure in the ventricle falls below that in the aorta. In actual fact, the pressure 'flip' occurs much earlier in ejection, and yet the valve remains open. This is because of the greater total fluid energy in the ventricle throughout ejection. Still others state or give the impression that mitral valve closure is totally dependent upon an increase of pressure in the left ventricle, when in reality the situation is much more complicated.



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