Hemostasis

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Definition

noun, plural: hemostases

The process of stopping or arresting bleeding or keeping the blood within the damaged blood vessel, particularly by physiological means such as vasoconstriction and coagulation or by surgical means


Supplement

Hemostasis is a process that stops or arrest bleeding. It helps keep the blood within the damaged blood vessel. This is the first stage of tissue repair and wound healing. Hemostasis involves three major stages: (1) vascular spasm or vasoconstriction, temporary blockage of a break by a platelet plug, and (3) blood coagulation (clot formation).

During vascular spasm or vasoconstriction, the blood vessels constrict. The smooth muscle cells in the damaged blood vessel constrict as an immediate reflex. This would reduce the blood flowing through the damaged blood vessel. Thus, it would hamper the progression of blood loss. Vasoconstriction is promoted when collagen from the injured site is exposed. The platelets adhere to the site and release cytoplasmic contents that promote vasoconstriction. Apart from vasoconstriction, the platelets also promote the formation of a platelet plug. The platelets express receptors that enable interacting with other platelets to aggregate and adhere to one another. This is referred to as primary hemostasis. Depending on the extent of injury, this may then be followed by clot formation. Blood clotting factors circulating through the bloodstream may interact and become activated through a coagulation cascade system that ends in the formation of a fibrin meshwork around the platelet plug. Certain blood cells may be trapped as well in this meshwork. The formation of clot around the platelet plug is referred to as secondary hemostasis.


Word origin: Greek, from aíma (blood) + stásis (stagnation)

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