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The Heart and Blood Vessels

The Heart and Blood Vessels - flow through the organs...

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The Heart and Blood Vessels The circulatory system includes the blood , heart and blood vessels . The cardiovascular components provide a pathway for pumped blood throughout the body. Circulatory Circuits The heart is a muscular organ that pumps blood to the lungs and throughout the body. Both sides (left and right) of the heart act as pumps. The right side of the heart pumps blood through the pulmonary trunk and arteries to the lungs where gas exchange occurs. This is known as the pulmonary circuit. In contrast, the left side of the heart pumps blood through the aorta to the head, arms, organs and legs of the body. This is the systemic circuit. At the level of the tissues, oxygen moves out of the blood and carbon dioxide moves into it. (See Figure 1). Figure 1 While the amount of blood flowing through the pulmonary circuit remains fairly constant, blood
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Unformatted text preview: flow through the organs, muscles and brain can vary dependent upon use. The systemic circuits are actually parallel pathways; blood can "choose" a particular branch, flow through that organ, and then head back to the heart. Blood flow through the various pathways is dynamic and may change to accommodate metabolic changes. For instance, during exercise the amount of blood directed to the digestive organs decreases while the amount of blood to the skeletal muscles increases. While the usual systemic pathway of blood is artery --> capillary bed --> vein, there are several portal systems in the body where blood flows from an artery --> capillary bed (where it picks up nutrients or hormones ) --> portal vein --> capillary bed (where it drops off nutrients or hormones) --> vein. (See Figure 2). Figure 2...
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