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Hemostasis: Difference between revisions
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== Three Steps of Hemostasis == | == Three Steps of Hemostasis == | ||
When a person's blood vessels are damaged, hemostasis begins its three steps to arrest bleeding. The three steps are ''' | When a person's blood vessels are damaged, hemostasis begins its three steps to arrest bleeding. The three steps are a '''vascular spasm''', a '''platelet plug''', and a '''coagulation'''. The explanation of a vascular spasm and a platelet plug is followed. However, the explanation of a coagulation will be located on a next section. | ||
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• A vascular spasm, a constriction of the damaged blood vessel, occurs at the site of injury. Vasoconstriction is initiated by the smooth muscle of the blood vessel in response to the injury and by nerve signals from pain receptors. | |||
• A platelet plug, consisting of a mass of linked platelets, fills the hole in the damaged blood vessel. Platelet plug formation follows these steps: | |||
a. Platelet adhesion. Platelets adhere to the exposed collagen fibers in the damaged blood vessel wall. | |||
b. Platelet release. Platelets release ADP (which attracts other platelets to the injury), serotonin (which stimulates vasoconstriction), and thromboxane A2 (which attracts platelets and stimulates vasoconstriction). Cellular extensions from the platelets interconnect and form a loose mesh. | |||
c. Platelet aggregation. Additional platelets arrive at the site of the injury in response to the released ADP and expand the accumulation of platelets. <br /> <ref>[http://www.cliffsnotes.com/study_guide/Hemostasis.topicArticleId-22032,articleId-21966.html Steps of Hemostasis] Unknown, Cliffnotes. <ref/> | |||
== Coagulation == | == Coagulation == | ||
