Medical Books and Lectures notes - Free downloads

When blood vessels are cut or damaged, the loss of blood from the system must be stopped before shock and possible death occur. This is accomplished by solidification of the blood, a process called coagulation or clotting. A blood clot consists of a plug of platelets enmeshed in a network of insoluble fibrin molecules. Platelet aggregation and fibrin formation both require the proteolytic enzyme thrombin . Clotting also requires: calcium ions (Ca 2+ )(which is why blood banks use a chelating agent to bind the calcium in donated blood so the blood will not clot in the bag). about a dozen other protein clotting factors . Most of these circulate in the blood as inactive precursors. They are activated by proteolytic cleavage becoming, in turn, active proteases for other factors in the system. By tradition, these factors are designated by Roman numerals. I find this somewhat confusing and will use Arabic numerals instead. Initiating the Clotting Process Damaged cells display a...