Coag 4.2 Primary Hemostasis

Hemostasis

1. Maintains bloods fluid state when vessels are intact '

2. Form a localized clot during vessel injury

Fibrinolysis

Clot breakdown after repair

Blood coagulation

clot formation

Vasoconstriction

triggered by serotonin and thromboxane A2

Antiplatelet

• Substance that prevents platelelets from sticking together and forming a clot

What are the factors of Anti platelet

Endothelium releases Nitric oxide (prevents platelets from sticking), produces PGI2 (inhibits activation of platelets), and ADPase breaks down ADP to prevent “calling signal” of platelets

What are the factors of anticoagulant

Thrombomodulin + protein c decreases thrombin production generation and slows clot generation, Heparan sulfate+ antithrombin stops clotting and fibrin formation, TFPI prevents the start of clotting

What are the factors of Profibronlytic

tPA = tissue plasminogen activator

What conditions does Antiplatelet, Anticoagulant, Profibrinolytic act?

Intact endothelium = non thrombogenic

What conditions does promote platelets, procoagulant, and antifibrinolytic act?

Endothelium injury = thrombogenic

What factors are in promoting platelets

vWF release + collagen exposure, PAF- Platelet activating factor, endothelin (vasoconstrictor)

What factors are in procoagulant

Tissue factor exposure/expression

What factor is in antifibrinolytic

PAI = 1 Plasminogen Activator Inhibitor - 1

laminin & fibronectin purpose

Cell attachment

Components of Platelet Ultrastructure

Organelle zone, membrane system, pheripheral zone, structural zone

Peripheral Zone components

• Glycocalyx and plasma membrane

• This place contains platelet surface receptors to detect injury

Structural zone components

• Cytoskeleton of microtubules and actin, maintains the resting discoid shape

• produces shape change during activation

Organelle zone components

• Releases granules during activation

• dense granules

• alpha granules

Dense granules

• ADP, calcium, serotonin

• Promote activation, aggregation, and vasoconstriction

Alpha granules

• vWF, fibrinogen, factor V, platelet factor 4

• Support adhesion, coagulation, and repair

Membrane Systems components

• Open canalicular system

• Dense tubular system

Open canalicular system (OCS)

• Connected to platelet surface

• route for granule release

• provides membrane for shape change

Dense tubular system (DTS)

• closed internal network

• stores Ca2+

• produce thromboxane A2

Thromboxane A2

• synthesized by activated platelets

• promotes platelet activation, recruitment, and vasoconstriction

Why is the storage of calcium important?

Calcium triggers platelet shape change, surface receptors and platelet aggregation. Basically the on switch for the platelets to change

Primary hemostatic plug formation steps

1. Adhesion 2. Activation and shape change 3. Secretion 4. Aggregation

Thrombin

Powerful platelet activator, produced during coagulation

ADP

• Released from platelet

• Promotes glycoprotein 2b/3a

Platelet Adhesion Steps

• Vessel injury exposes collagen

• vWF binds to collagen

• Plt GP1b/ IX/ V binds vWF, tethering the plt

• Plt GPVI and GPIa/IIa bind collagen

  • Strengthens adhesion

  • promotes activation

Platelet Adhesion Components

• vWF- binds collagen and platelet GpIb/IX/V

• Stored in

  • Endothelial Weibel-Palade bodies

  • platelet alpha granules

• Glycoproteins