Platelets Flashcards
Function of platelets
They form the primary haemostatic plug
They provide a phospholipid surface on which clotting factors an work
They cross link the fibrin clot to make it stable
Where are platelets derived from?
HSCs
What I the sunendithelial matrix made of ?
Collegen
VWF
Tissue factors
What activates coagulation
A breach in the endothelium - expose subendithelial matrix. VWF unfolds.
Always little bit happening- more in trauma
What does VWF do?
Grab platelets
VWF has receptors for platelets & vice versa
What happens when platelets bind VWF?
Ps become activated Change shape Bind to more things Release contents (granules) G= dense bodies & a granules
What do granules do?
Attract platelets
Attract more platelets
Attract VWF
What dos fibrin do?
It’s a glue!
Glues the platelet plug following activation if coagulation cascade
What activates platelets?
Thrombin from CC
ADP released from dense bodies
Collagen in vessel wall
Platelets
Platelet activation causes:
A shape change Formation of pseudopodia Granule release Platelet attraction & aggregation Provide phospholipid be on which CC can work
What do platelets bind to to form a table thrombus?
VWF
Collagen
Fibrin
How can platelets go wrong?
To many/few
Poor quality = abnormal function
Name an squired cause of a qualitative disorders of platelet function
Myelodysplasia
Bone marrow failing- cells produced are poor quality & low in number
What drugs can interfere with platelets
Aspirin
NSAIDs
Clopidogrel
What type of antagonist is clopidogrel?
P2Y12
What enzyme does aspirin inhibit?
COX 1
Stops formation of thromboxin A2
Name a congenial platelet disorder where they cannot bind to VWF
Bernard Soulier
Autosomal recessive
Rare
What congenital condition causes lack of platelet aggregation this no platelet plug?
Glanzmann’s thrombasthenia
What disease causes abnormal release of granules?
Pool disorders
What is mucocutaneous bleeding?
Bleeding from mucous membranes
What’s the normal platelet count?
150-450 ✖️ 10 power 9/ L
What is thrombocytopenia?
Not enough platelets!! ❤️⬇️
< 150
What is thrombocytosis?
Too many platelets! ❤️❤️❤️⬆️
> 500
Causes of ⬆️ platelets (thrombocytosis)
Smoking
Splenectomy
Cancer
Iron deficiency
What is the physiological cause of thrombocytosis?
Cytokine storm…..
Increase megakaryocytes
What gene is mutated in Wiskott-Aldrich syndrome?
WAS gene
Causes defective actin polymerisation
X-linked recessive
Symptoms of W-A syndrome?
Thrombocytopenia
Eczema
What cells are found in bone marrow?
Lots of fat cells
Megakaryocytes
Myeloid precursor cells
What condition causes bone marrow to become packed with plasma cells?
Myeloma
Can’t produce RBCs/WBCs/platelets
What suppresses bone marrow?
Chemotherapy
Leukopenia
⬇️ WBCs
What conditions cause ⬇️ platelets?
Glandular fever Hypersplenism Liver cirrhosis Massive Haemorrhage Sepsis Immune
What is the blood picture with increased consumption?
Low platelets
Normal or high WBCs
Low or normal RBCs
Name some secondary causes of autoimmune thrombocytopenia
Autoimmune conditions (SLE, RA) Drugs (penicillin, quinine, abciximab, heparin) Viral infections (HIV, hep C & B)
Name the primary cause of autoimmune thrombocytopenia
I idiopathic immune thrombocytopenia
What is the only thing in the blood picture that is affected in ITP?
Platelets (reduced)
What is ITP
Primary autoimmune thrombocytopenia
What is the peak age incidence for acute & chronic ITP?
A = 2-8
C = older
What causes purpuric rash?
Leaky endothelia
Treatment for ITP
1) Corticosteroids, Ig, platelets
2) splenectomy, immunosuppression, anti-CD20 antibody
3) thrombopoietin agonist/ mimetics
What produces thrombopoietin?
The liver
Why does TPO bind to?
Megakaryocytes & platelets
Normal Hb for women
11.5-15.5
If platelet count goes below 10 what is probable cause?
Immune mediated
