MEDizzy - A 19-year-old male severs an artery in a motorcycle

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Cardiovascular Physiology

A 19-year-old male severs an artery in a motorcycle accident. A bystander applies a tourniquet to stop the bleeding. When the paramedics arrive, the blood pressure of the injured man was only slightly hypotensive and his pupils were reactive. The greatest percentage of the redistributed blood volume came from which of the following?

ExplanationThe total circulating blood volume is approximately 70 mL/kg, about two-thirds of which is found in the systemic veins and venules. A significant volume of blood (15%) is found in the pulmonary circulation. The large volume of blood found on the venous side of the circulation is used to adjust circulating blood volume. For example during hemorrhage, contraction of the veins and venules of the skin increases the amount of blood available for perfusion of the heart and brain.