Blood plateletsBlood platelets
ThrombocytesThrombocytes
Small granulated oval or round bodiesSmall granulated oval or roun...
Factor helping formation of thromboplastinsFactor helping formation of thromboplastins
Factor helping prothrombin –thrombi...
HaemostasisHaemostasis
Prevention of blood loss from blood vessels. bleeding is stopped byPrevention of blood loss from bl...
33--Blood coagulationBlood coagulation
The clot begin to develop inThe clot begin to develop in 15-20 second if the trauma...
Platelets
Platelets
Platelets
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Platelets

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Platelets

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Platelets

  1. 1. Blood plateletsBlood platelets ThrombocytesThrombocytes Small granulated oval or round bodiesSmall granulated oval or round bodies FormationFormation;; They are fragments of megakaryocytes which are giant cell present in the boneThey are fragments of megakaryocytes which are giant cell present in the bone marrowmarrow.. One megakaryocyte →4000 plateletsOne megakaryocyte →4000 platelets.. Count ;Count ; 1/4-1/2 million per mm31/4-1/2 million per mm3.. Platelets have mucopolysaccharide surface coat which is import ants inPlatelets have mucopolysaccharide surface coat which is import ants in platelets adhesion &aggregationplatelets adhesion &aggregation.. Function of plateletsFunction of platelets;; Haemeostasis:Haemeostasis: which means the various steps which stop bleedingwhich means the various steps which stop bleeding These steps areThese steps are 11--marked constriction of the injured vessels:marked constriction of the injured vessels: due to release ofdue to release of vasoconstrictor substance called serotonin or 5 hydroxytrytamine by plateletsvasoconstrictor substance called serotonin or 5 hydroxytrytamine by platelets 22--platelets then adhere and plug the vessel openingplatelets then adhere and plug the vessel opening 33--blood coagulation:blood coagulation: platelets are very sticky bodies ,they stick to theplatelets are very sticky bodies ,they stick to the edge of injury vessels and disintegrate, releasing the following factor which helpedge of injury vessels and disintegrate, releasing the following factor which help blood coagulationblood coagulation..
  2. 2. Factor helping formation of thromboplastinsFactor helping formation of thromboplastins Factor helping prothrombin –thrombin reaction.Factor helping prothrombin –thrombin reaction. Factor helping fibrinogen –fibrin reaction .Factor helping fibrinogen –fibrin reaction . Factor with anti -heparin activity.Factor with anti -heparin activity. 4-4- Clot retraction IT mean contraction of fibrin threads of the clot.IT mean contraction of fibrin threads of the clot. Clot retraction makes the clot firm and if occurs inside theClot retraction makes the clot firm and if occurs inside the vessels it may open the vessels again after being closed byvessels it may open the vessels again after being closed by clot.clot. 5- phagocytosis Platelets can phagocyte particles as carbon and viruses.Platelets can phagocyte particles as carbon and viruses. 6- Storage and transport; Platelets store and transport serotoninPlatelets store and transport serotonin
  3. 3. HaemostasisHaemostasis Prevention of blood loss from blood vessels. bleeding is stopped byPrevention of blood loss from blood vessels. bleeding is stopped by several mechanismsseveral mechanisms which are : 1- Local vasoconstriction ;immediately after injury which is due to;;immediately after injury which is due to; _-liberation of serotonin and other vasoconstrictors substance from_-liberation of serotonin and other vasoconstrictors substance from platelets which adhere to the wall of the damage vessels .platelets which adhere to the wall of the damage vessels . - local myogenic contraction of the blood vessel initiated by direct damage- local myogenic contraction of the blood vessel initiated by direct damage of the vascular wall, which cause by transmission of action potentials alongof the vascular wall, which cause by transmission of action potentials along the vessels wall for several centimeters and results in constriction of thethe vessels wall for several centimeters and results in constriction of the vessels.vessels. 2- Formation of platelet plug: -As a results of injury the sub endothelial collagen fibers are exposed-As a results of injury the sub endothelial collagen fibers are exposed ,binding of platelets with collagen initiate platelets activation .,binding of platelets with collagen initiate platelets activation . -The activated platelets swell, develop pseudopodia, become sticky and-The activated platelets swell, develop pseudopodia, become sticky and discharge their content including ADP.discharge their content including ADP. -The released ADP activate the nearby platelets, this stick to originally-The released ADP activate the nearby platelets, this stick to originally activated platelets (platelets aggregation )activated platelets (platelets aggregation ) And also release ADP which activate more and more platelets.And also release ADP which activate more and more platelets. -Thus the vicious cycle of platelets activation occur which lead to form a-Thus the vicious cycle of platelets activation occur which lead to form a loose platelets plug which can usually stop bleeding from small wound .loose platelets plug which can usually stop bleeding from small wound .
  4. 4. 33--Blood coagulationBlood coagulation The clot begin to develop inThe clot begin to develop in 15-20 second if the trauma to thesecond if the trauma to the vascular wall is sever and invascular wall is sever and in 1-2 minutes if the trauma is minorminutes if the trauma is minor Activator substance both from the traumatized vascular wallActivator substance both from the traumatized vascular wall and from platelets adhere to vascular wall initiate the clottingand from platelets adhere to vascular wall initiate the clotting mechanism.mechanism. Within 3-6 minutes after ruptures of the vessels is filled withWithin 3-6 minutes after ruptures of the vessels is filled with clot .clot . After 30 minutes to an hours the clot retract .this close theAfter 30 minutes to an hours the clot retract .this close the vessels.vessels. As the clot retract it pull the edge of injured vessels togetherAs the clot retract it pull the edge of injured vessels together helping homeostasishelping homeostasis ..
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