Question

Explain the evolution on the thoughts of the ciculatory system. Who were the major players? What were the major changes in through from person to person. Start with Hippocrates and move through the end of the Renaissance with William Harvey.

Answer 1

Most animals are complex, multicellular organisms that require a mechanism for transporting nutrients throughout their bodies and for removing waste products. The circulatory system has evolved over time from simple diffusion through cells, in the early evolution of animals, to a complex network of blood vessels that reach all parts of the human body. This extensive network supplies the cells, tissues, and organs with oxygen and nutrients, while removing carbon dioxide and waste, the byproducts of respiration. The circulatory system can be thought of as a highway system that runs throughout the body.

At the core of the human circulatory system is the heart. The size of a clenched fist, the human heart is protected beneath the rib cage. Made of specialized and unique cardiac muscle, it pumps blood throughout the body and to the heart itself. Heart contractions are driven by intrinsic electrical impulses that the brain and endocrine hormones help to regulate. Understanding the heart’s basic anatomy and function is important to understanding the body’s circulatory and respiratory systems.

Gas exchange is one essential function of the circulatory system. A circulatory system is not needed in organisms with no specialized respiratory organs, such as unicellular organisms, because oxygen and carbon dioxide diffuse directly between their body tissues and the external environment. However, in organisms that possess lungs and gills, oxygen must be transported from these specialized respiratory organs to the body tissues via a circulatory system. Therefore, circulatory systems have had to evolve to accommodate the great diversity of body sizes and body types present among animals.

• A closed circulatory system, found in all vertebrates and some invertebrates, circulates blood unidirectionally from the heart, around the body, and back to the heart.
• An open circulatory system, found in arthropods, pumps blood into a cavity called a hemocoel where it surrounds the organs and then returns to the heart(s) through ostia (openings).
• The blood found in arthropods, a mix of blood and interstitial fluid, is called hemolymph.

Although Hippocrates has been traditionally recognized as the father of medicine and one of the major early writers regarding the cardiovascular system, very little is known of about the knowledge of the cardiovascular system in the pre-Hippocratic period.Pre-Hippocratic medicine was largely based on religious beliefs and not in scientific observations. Interestingly, despite these erroneous methods, the pre-Hippocratics were able to identify pipes carrying air into the body and name the air carriers (arteries). Unfortunately, the arteries were not associated with blood but rather with air, however, this ancient word still remains in use in our days. This paper reviews the evolution of thinking and discovery regarding the different aspects of the cardiovascular system in the pre-Hippocratic era.

Harvey had proved that the venous blood flowed to the heart, and that the body's valves in the veins maintained the one-way flow.He contributed to human knowledge by being the first to describe the human circulatory system in a detailed and systematic way. He did this by starting with a detailed study of blood flows into and out of the heart.

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