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Hemostasis

Hemostasis is the process of stopping bleeding, occurring in three stages: vasoconstriction, platelet plug formation, and blood coagulation. Initially, blood vessels constrict to reduce blood loss, followed by platelets adhering to the damaged area and forming a temporary plug. Finally, coagulation occurs where fibrin is formed, solidifying the platelet plug and preventing further bleeding.

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5 views1 page

Hemostasis

Hemostasis is the process of stopping bleeding, occurring in three stages: vasoconstriction, platelet plug formation, and blood coagulation. Initially, blood vessels constrict to reduce blood loss, followed by platelets adhering to the damaged area and forming a temporary plug. Finally, coagulation occurs where fibrin is formed, solidifying the platelet plug and preventing further bleeding.

Uploaded by

shreyaanbhule06
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Hemostasis

19
DEFINITION
STAGES OF HEMOSTASIs
VASOCONSTRICTION
PLATELET PLUG FORMATION
cOAGULATION OF BLOOD

DEFINITION platelets to the collagen is accelerated by von Willebrand


Hemostasis is defined as arrest or stoppage of bleeding actor. nis tactor acts as a bridge between a specific
glycoprotein present on the surface of platelet and
collagen fibrils.
STAGES OF HEMOSTASIS
When a blood vessel is injured, the injury initiates a PLATELET PLUGFORMATION
series of reactions, resulting in hemostasis. It occurs in Platelets get adhered to the collagen of ruptured blood
three stages (Fig. 19.1): vessel and secrete adenosine diphosphate (ADP) and
1. Vasoconstriction
2. Platelet plug formation thromboxane A These two substances attract more and
Coagulation of blood. more platelets and activate them. All these platelets aggre
gate together and forma loose temporary platelet plug or
VASOcONSTRICTION temporary hemostatic plug, which closes the ruptured
vessel and prevents further blood loss. Platelet aggrega
Immediately after injury. the blood vessel constricts tion is accelerated by platelet-activating factor (PAF).
and decreases the loss of blood from damaged
portion. Usually, arterioles and small arteries constrictCOAGULATION OF BLOOD
Vasoconstriction is purely alocal phenomenon. vwie Durion this process. the fibrinogen is converted into
Diood vesseis are cut, ne enoonelum is damaged and fibrin. Fibrin threads get attached to the loose platelet
Oen and ge activated. The activated platelets secrete plug. which blocks the ruptured part of blood vessels
serotonin and other vasoconstrictor substances which and prevents further blood loss completely. Mechanism
cause constriction of the blood vessels. Adherence of of blood coagulation is explained in the next chapter.

128 Section 2 Blood and Body Fluids

Injury to the biood vessel and damage of endothelium

Exposure of collagen
von Willebrand factor

Adherence of platelets to collagen

Activation of platelets

Secretion of serotonin Secretion of ADP and Formation of


thromb0xane A prothrombin activator

PAI

Aggregatb

Vasoconstriction Platelet plug Blood clotting


formation

Stage Stage 2 Stage 3

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