Primary Haemostasis & Platelet Pathology – Ultimate Flashcards (16)

Structural difference between Hemostasis and Homeostasis

• Haemostasis: Balance between procoagulant (clotting) and anticoagulant (fluid) mechanisms to prevent blood loss.

• Homeostasis: General maintenance of stable internal conditions.
  (Tip: Keep focus on “blood-specific vs general bodily balance.”)

Platelet production and regulation

• Produced in: Bone marrow from megakaryocytes.

• Regulated by: Thrombopoietin (TPO).

Platelet granules and contents

• Alpha-granules: vWF, Fibrinogen, Factor V (clotting proteins).

• Dense-granules: ADP, ATP, Serotonin, Calcium (signaling molecules).

How platelets increase surface area during activation

• Mechanism: Open Canalicular System (invaginated membranes) → rapid granule release and more coagulation surface.

Dual role of von Willebrand Factor (vWF)

Adhesion: Binds platelets to exposed collagen, Stabilization: Protects Factor VIII from degradation in plasma.

Type 1 vs Type 2 von Willebrand Disease (vWD)

• Type 1: Quantitative deficiency → not enough vWF.

Type 2: Qualitative defect → vWF present but dysfunctional.

Why vWD can prolong APTT

Low vWF → Factor VIII degraded faster → intrinsic pathway slowed → prolonged APTT.

Bernard-Soulier Syndrome

• Defect: GPIb receptor deficiency → platelets cannot adhere to vessel wall.

Glanzmann’s Thrombasthenia

Defect: GPIIb/IIIa receptor deficiency → platelets cannot aggregate.

Antiplatelet drugs: Aspirin vs Clopidogrel

• Aspirin: Inhibits Thromboxane A2 via COX-1.

• Clopidogrel: Blocks platelet ADP receptor → prevents aggregation.

Storage Pool Disorder

• Platelets lack granules (alpha or dense) or cannot release them → defective function.

Characteristic skin sign of platelet disorders

Petechiae: Pinpoint red/purple spots from minor capillary bleeding.

what is Platelet lifespan

• ~7–9 days in circulation.

whta is the Importance of platelet negative charge

Activated platelets expose negatively charged phospholipids → scaffold for coagulation cascade.

First vascular response to injury

Vasoconstriction: Mediated by Thromboxane A2 and Endothelin → reduces blood flow.

what is Pre-surgery vWD treatment

Desmopressin (DDAVP): Triggers endothelial release of stored vWF.