Download Platelets

Platelets/
megakaryocytes
Normal value: 1.5-4 lakh cells/cumm of
blood.
Size : 1.5-3 microns
Life span : 8-12 days
Destruction by spleen
Structure of platelets
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Small anucleate cells
Highly developed cytoskeletal system
Granulated
Extensive microtubules and microfilaments
Frequently change shape with very long thin
processes extending out called filopodia.
Cell membrane
• Exterior glycocalyx coat
• Negative charge on the surface due to sialic
acid residues along with glycoproteins prevent
adherence to each other and endothelium.
• Open canalicular systems
• Dense tubular systems
• Platelet granules
- alpha granules
- dense granules
Variations :
Thrombocytosis.
Splenectomy.
After trauma: surgery ,injury ,child birth.
Adminstration of epinephrine.
Stress .
Thrombocytopenia:
Bone marrow depression.
Hypersplenism
Viral infection Eg: Dengue fever.
Drug hypersensitivity
Functions of platelets:
Hemostasis: Temporary platelet plug.
Blood coagulation: Release clotting platelet
Factor 4, V, XI, XIII PL ,HMWK.
Clot retraction
Thrombolysis
Phagocytic function:
Storage and transport function:
Vasoconstriction
Wound healing and vascular growth :
Platelet derived growth factor
Platelet disorder:
A. Thrombocytopenia:
Reduction in the platelet count secondary
to some other cause.
B . Idiopathic thrombocytopenia:
Reduction in the number of platelets due
to unknown cause.
C. Thromboasthenia :
Defective platelet function.