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The Heart and the Circulatory System



William Harvey - Father of Cardiovascular Medicine

William Harvey was born in 1578 in Folkstone, England. The eldest of seven sons, Harvey received a Bachelor of Arts degree from Cambridge in 1597. He then studied medicine at the University of Padua, receiving his doctorate in 1602. By all measures, Harvey was successful. After he finished his studies at Padua, he returned to England and set up practice. He then married Elizabeth Brown, daughter of the court physician to Queen Elizabeth I and King James I. This put in him in position to be noticed by the aristocracy, and Harvey quickly moved up the ladder. Eventually, he became court physician to both King James I and King Charles I.

While acting as court physician, Harvey was able to conduct his research in human biology and physiology. Harvey focused much of his research on the mechanics of blood flow in the human body. Most physicians of the time felt that the lungs were responsible for moving the blood around throughout the body. Harvey questioned these beliefs and his questions directed his life-long scientific investigations.

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Harvey's experiments involved both direct dissection and physiological experiments on animals. His observations of dissected hearts showed that the valves in the heart allowed blood to flow in only one direction. Direct observation of the heartbeat of living animals showed that the ventricles contracted together, dispelling Galen's theory that blood was forced from one ventricle to the other. Dissection of the septum of the heart showed that it contained arteries and veins, not perforations. When Harvey removed the beating heart from a living animal, it continued to beat, thus acting as a pump, not a sucking organ. Harvey also used mathematical data to prove that the blood was not being consumed. Removal of the blood from human cadavers showed that the heart could hold roughly two ounces of blood. By calculating the number of heartbeats in a day and multiplying this by two ounces, he showed that the amount of blood pump far exceeded the amount that the body could possibly make. He based this figure on how much food and liquids a person could consume. To Harvey, this showed that the teaching by Galen that the blood was being consumed by the organs of the body was false. Blood had to be flowing through a 'closed circuit' instead. Even though he lacked a microscope, Harvey theorized that the arteries and veins were connected to each other by capillaries, which would later be discovered by Marcello Malpighi some years after Harvey's death.

Harvey did not let the beliefs of Galen concerning the role of natural, vital, and animal spirits and their effects on physiology affect his objectivity. Instead, Harvey asked simple, pointed questions, the types of questions that even today are the hallmark of good scientific research. Harvey asked such questions as why did both the lungs and the heart move if only the lungs were responsible for causing circulation of blood? Why should, as Galen suggested, structurally similar parts of the heart have very different functions? Why did 'nutritive' blood appear so similar to 'vital' blood? These, and other, questions gave Harvey his focus.

Harvey's lecture notes show that he believed in the role of the heart in circulation of blood through a closed system as early as 1615. Yet he waited 13 years, until 1628, to publish his findings in his work Exercitatio anatomica de motu cordis et sanguinis in animalibus or On the Movement of the Heart and Blood in Animals. Why did he wait so long? Galenism, or the study and practice of medicine as originally taught by Galen, was almost sacred at the time Harvey lived. No one dared to challenge the teachings of Galen. Like most physicians of his day, William Harvey, was trained in the ways of Galen. Conformation was not only the norm, but was also the key to success. To rebel against the teachings of Galen could quickly end the career of any physician. Perhaps this is why he waited.

Harvey's hesitation proved well-founded. After his work was published, many physicians and scientists rejected him and his findings. Using different assumptions of the amount of blood contained in the heart, scientists argued that the blood could indeed be consumed. Controversy raged for a full twenty years after publication of "On the Movement of the Heart and Blood in Animals." Yet, with time, more and more physicians and researchers accepted Harvey's hypotheses.

Like all good research, Harvey's work raised more questions than it answered. For example, if blood was not consumed by organs, how did different parts of the body obtain nourishment? If the liver did not make blood from food, where did blood originate? These questions, and others like them, directed the research of many investigations for many years to come. Medical practice in Harvey's time, however, changed little. Even though the mechanics of blood flow were understood now, the understanding of the causes of many diseases were still bathed in the mystery of spirits. In fact, the practices of bleeding, lancing, and leeching increased in the years following Harvey's work. On the positive side, medicine did make some advances, for it was during the seventeenth century that administering medicine through intravenous injections came into practice.

William Harvey's classic work became the foundation for all modern research on the heart and cardiovascular medicine. It has been said that Harvey's proof "of the continuous circulation of the blood within a contained system was the seventeenth century's most significant achievement in physiology and medicine." Further, his work is considered to be one of the most important contributions in the history of medicine. Without the understanding of the circulatory system made possible by Harvey's pioneering work, the medical miracles that we think are commonplace would be impossible. Let's take a few moments to discuss the hearts and circulatory systems found in a variety of animals.

Next page > The Heart and the Circulatory System > William Harvey > Types of Circulatory Systems > Anatomy of the Heart > The Pulmonary and Systemic Circuits > The Blood Vessels > Circulatory Problems > Modern Cardiovascular Medicine



Source: Carolina Biological Supply/Access Excellence
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