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Hemostasis occurs when blood is present outside of the body or blood vessels. It is the innate response for the body to stop bleeding and loss of blood. During hemostasis three steps occur in a rapid sequence. Vascular spasm is the first response as the blood vessels constrict to allow less blood to be lost.
This process is often called "primary hemostasis". [19] Coagulation cascade: It is a series of enzymatic reactions that lead to the formation of a stable blood clot. The endothelial cells release substances like tissue factor, which triggers the extrinsic pathway of the coagulation cascade. This is called as "secondary hemostasis". [20]
The coagulation cascade of secondary hemostasis. Under homeostatic conditions, the body is maintained in a finely tuned balance of coagulation and fibrinolysis. The activation of the coagulation cascade yields thrombin that converts fibrinogen to fibrin; the stable fibrin clot being the final product of hemostasis. The fibrinolytic system then ...
Compared to other smaller vessels in the body, the artery has a much bigger diameter (4 mm), therefore the resistance is low. [ 25 ] The arm–leg (blood pressure) gradient is the difference between the blood pressure measured in the arms and that measured in the legs.
A thrombus (pl. thrombi), colloquially called a blood clot, is the final product of the blood coagulation step in hemostasis. There are two components to a thrombus: aggregated platelets and red blood cells that form a plug, and a mesh of cross-linked fibrin protein. The substance making up a thrombus is sometimes called cruor.
Some medical conditions can also make patients susceptible to bleeding. These are conditions that affect the normal hemostatic (bleeding-control) functions of the body. Such conditions either are, or cause, bleeding diatheses. Hemostasis involves several components.
The human body needs iron for oxygen transport. Oxygen (O 2) is required for the functioning and survival of nearly all cell types. Oxygen is transported from the lungs to the rest of the body bound to the heme group of hemoglobin in red blood cells. In muscles cells, iron binds oxygen to myoglobin, which regulates its release.
Under normal physiological conditions, blood flows through the body without any noticeable aggregation of platelets. This is because platelets are not initially programmed to accumulate by themselves because this could cause an undesirable thrombosis. However, during hemostasis, coagulation is desired.