<Li> Cardiac shunt is an unnatural connection between parts of the heart that leads to blood flow that bypasses the lungs . </Li> <P> The discovery of pulmonary circulation has been attributed to several scientists over the years . In much of modern medical literature, the discovery is credited to English physician William Harvey (1578 - 1657 CE). Other sources credit Spanish physician Michael Servetus (c. 1509 - 1553 CE) and Arab physician Ibn al - Nafis (1213 - 1288 CE) with the discovery . However, the first descriptions of the cardiovascular system came before these men . </P> <P> The earliest known description of the role of air in circulation was produced in Egypt in 3500 BCE . At this time, Egyptians believed that the heart was the origin of many channels that connected different parts of the body and transported air as well as urine, blood, and the soul . The Edwin Smith Papyrus (1700 BCE), named for American Egyptologist Edwin Smith (1822 - 1906 CE) who purchased the scroll in 1862, provided evidence that Egyptians believed that the heartbeat created a pulse that transported the above substances throughout the body . A second scroll, the Ebers Papyrus (c. 1550 BCE), also emphasized the importance of the heart and its connection to vessels throughout the body and described methods to detect cardiac disease through pulse abnormalities . However, despite their knowledge of the heartbeat, vessels, and pulse, the Egyptians attributed the movement of substances throughout the vessels to air that resided in these channels, rather than to the heart's force . The Egyptians knew that air played an important role in circulation, but they did not yet have a concept for the precise role of the lungs . </P> <P> The next addition to the human understanding of pulmonary circulation came with the Ancient Greeks . The physician Alcmaeon (520 - 450 BCE) proposed that the brain, not the heart, was the connection point for all of the vessels in the body . He believed that the function of these vessels was to bring the spirit (pneuma) and air to the brain . Empedocles (492 - 432 BCE), a philosopher, proposed a series of pipes impermeable to blood but continuous with blood vessels which carried the pneuma throughout the body . He proposed that this spirit was internalized with pulmonary respiration . The physician Hippocrates (460 - 370 BCE) developed the view that the liver and spleen produced blood, which traveled to the heart to be cooled by the lungs that surrounded it . Hippocrates described the heart as having two ventricles connected by an interventricular septum . He depicted the heart as the connecting point for all the vessels of the body and proposed that some vessels carried only blood, while others also carried air . These air - carrying vessels were the pulmonary veins, which brought air to the left ventricle, and the pulmonary artery, which carried air to the right ventricle and blood to the lungs . He also proposed two atria of the heart that functioned to capture air . Hippocrates was one of the first to begin to accurately describe the anatomy of the heart and to describe the involvement of the lungs in circulation, but his descriptions of the process of pulmonary circulation and of the functions of the parts of the heart were still largely incorrect . </P>

Where does deoxygenated blood re enter the heart