Lecture 8: Platelets in health and disease Flashcards
What cells produce platelets?
- megakaryocytes (originate from megakaryoblasts)
- They have multi-lobed nuclei
- Process is called thrombocytopoiesis
What are the factors in thrombocytopoiesis?
- Steel factor
- LIF
- Interleukins 6 & 11
- Thrombopoietin (TPO)
Figures of platelet homoeostasis?
- Require 40000/uL/per day
- life span 7-10 days
Platelet ultrastructure
- contain granules
- Electron dense
- a-granules; coagulation factors
What is primary haemostasis?
- Process of forming a platelet plug at the site of vessel injury
- Initial phase involves vascular constriction
- Then platelets activated, aggregate –> loose platelet plug
What factor is involved in recruitment of platelets?
-Von Willebrand factor
What is exposed that allows platelet adherence in vessel damage?
- Collagen which binds to VWF via glycoprotein receptor 1B-V-IX
- Activation of prostagladins synthesis
Once GP- 1B-V-IX activated what happens to the platelet?
- Changes shape and expresses intergrin a(2B)B(3)
- These then use other proteins e.g fibrinogen to adhere to other platelets
In 4 simple words starting with injury describe the steps of platelet clotting?
- Injury
- Initiation
- Extension
- Stabilization
What does activated prostagladin synthesis after platelet adherence to collagen produce?
- Thromboxane A2
- This causes release of granules from platelets –> aggregation
How does aspirin affect platelets?
-Stops cyclo-oxygenase activity which stops arachidonic acid –> prostaglandins —> decreased thromboxane A2
What factors help platelet aggregation grow and knit together more tightly?
- PLC
- PKC
- PI3K
How can platelet production be reduced?
- viral infection
- Drugs
- Bone marrow failure
How can platelet destruction occur?
- immune thrombocytopenia
- DIC
- drugs
- viral infection
How can platelet production be increased?
-myeloproliferative neoplasms
