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Unformatted text preview: Hemostasis Hemostasis, the stoppage of bleeding, is accomplished through three steps: • 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: 1. Platelet adhesion. Platelets adhere to the exposed collagen fibers in the damaged blood vessel wall. 2. Platelet release. Platelets release ADP (adenosine diphosphate, which attracts other platelets to the injury), serotonin (which stimulates vasoconstriction), and thromboxane A 2 (which attracts platelets and stimulates vasoconstriction, and keeps the platelets “sticky” so they continue to adhere to the injured site). Cellular extensions from the platelets they continue to adhere to the injured site)....
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- Spring '10
- Platelets, Blood vessel, Platelet adhesion. Platelets, Platelet release. Platelets