User:Medicusfuturi/Galen

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This article seems relatively well put together. However, it could use more information regarding Galen's exact contributions to the cardiovascular system in addition to what is already listed.

Galen contributed a substantial amount to the understanding of pathology. Under the Hippocratic bodily humors theory, differences in human moods come as a consequence of imbalances in one of the four bodily fluids: blood, yellow bile, black bile, and phlegm. Galen promoted this theory and the typology of human temperaments. In Galen's view, an imbalance of each humor corresponded with a particular human temperament (blood – sanguine, black bile – melancholic, yellow bile – choleric, and phlegm – phlegmatic). Thus, individuals with sanguine temperaments are extroverted and social; choleric people have energy, passion, and charisma; melancholics are creative, kind, and considerate; and phlegmatic temperaments are characterized by dependability, kindness, and affection. Many theorist just like Galen believed that sickness came from an imbalance in the body and that the best way to treat an imbalance was by bleeding, enemas, and vomiting. However, the practice of blood letting is rarely used today (see treatment of Hemochromatosis).

Among Galen's major contributions to medicine was his work on the circulatory system. Before Galen's research, it was believed that the arteries carry oxygen rather than blood. He was the first to recognize that there are distinct differences between venous (dark) and arterial (bright) blood. In addition to these discoveries, Galen postulated much more about the nature of the circulatory system. He believed that blood originated in the liver, which follows the teachings of Hippocrates. The liver converted nutrients gathered from ingested food into blood to be used in the circulatory system. The blood created in the liver would eventually flow unidirectionally into the right ventricle of the heart via the great vein. Galen also proposed a theory on how blood receives oxygen from the lungs to be distributed throughout the body. He declared that the venous artery carried air from the lungs into the left ventricle of the heart to mix with created blood from the liver. This same venous artery allowed for an exchange of waste products from the blood back into the lungs to be exhaled. In order to receive air from the lungs in the left ventricle, the new blood needed to get there from the right ventricle. Thus, Galen asserted that there are small holes in the septum dividing the left and right sides of the heart; these holes allowed the blood to pass through easily to receive air and exchange the aforementioned waste products. Although his anatomical experiments on animal models led him to a more complete understanding of the circulatory system, nervous system, respiratory system, and other structures, his work contained scientific errors. Galen believed the circulatory system to consist of two separate one-way systems of distribution, rather than a single unified system of circulation. He believed venous blood to be generated in the liver, from where it was distributed and consumed by all organs of the body. He posited that arterial blood originated in the heart, from where it was distributed and consumed by all organs of the body. The blood was then regenerated in either the liver or the heart, completing the cycle. Galen also believed in the existence of a group of blood vessels he called the rete mirabile in the carotid sinus. Both of these theories of the circulation of blood were later (beginning with works of Ibn al-Nafis published ca. 1242) shown to be incorrect.