Lecture 22 Platelet Disorders Flashcards
What are the 4 main components platelets are made from?
Platelet made up of 4 main components:
1) Plasma membrane
2) Submembranous filaments
3) Peripheral Microtubules
4) Organelles most importantly the α and dense granules
Describe what the platelet plasma membrane is made up of?
Plasma Membrane: contains glycoproteins which are important to adhesion and aggregation. Also contain PF3 (phospholipids) which provide a surface for coagulations factors of the intrinsic and extrinsic pathways. Open canalicular system (OCS) provides large area of absorption of plasma factors.
What are responsible for platelets discoid shape, pseudopod formation and clot retraction? What is another function they do?
Microtubules and microfilaments are responsible for the discoid shape, pseudopod formation, and clot retraction. This area also responsible for movement of organelles toward surface of platelet
What are microtubules made of and how is it arranged? What do they do?
Microtubules:
1. Composed of subunits of tubulin parallel the platelet cell membrane and maintain the platelet discoid shape
2. Move inward on platelet activation to release α-granule contents and reassemble during platelet shape change to provide rigidity to pseudopods
What do microfilaments, microtubules and intermediate filaments do in platelets?
Microtubules, actin microfilaments and intermediate filaments control platelet shape change, extension of pseudopods, and secretion of granule contents
What organelles are in platelet cytoplasm?
Organelles: are the major portion of platelet cytoplasm. The structures include, mitochondria, dense bodies (granules), α (alpha) granules.
What are the 3 categories of platelet bleeding disorders?
- Decreased production
- Increased destruction.
- Defective function.
What acquired conditions result in decreased platelet production?
Viral Infections
Drug toxicity
Chemicals
Alcohol
Uremia
Bone marrow failure
What hereditary conditions result in thrombocytopenia?
Hereditary Thrombocytopenia
1. May-Hegglin
2. Wiskott-Aldrich
3. Bernard Soulier
Above conditions also have structural and functional defects.
Name some immune condition causes of platelet destruction?
Immune
1. Immune & idiopathic thrombocytopenic purpura (ITP)
2. Alloantibodies; neonatal and post transfusion
3. Autoantibodies (ie from Lupus and CLL)
4. Heparin induced thrombocytopenia (HIT)
5. Drugs
List the microangiopathic hemolytic anemias that result in platelet destruction.
Microangiopathic hemolytic anemias
- DIC
- TTP
- HUS
- HELLP
What impact can surgery have on platelets?
Consumption due to surgery.
What are two types of platelet function disorders?
Hereditary and
Acquired
See slide 13 for an overview list.
List conditions (4) that have platelet defects of adhesion.
Bernard-Soulier
Uremia
DIC
Paraproteinemias
List conditions (4) that have platelet defects of adhesion.
Bernard-Soulier
Uremia
DIC
Paraproteinemias
What type of defect do these two conditions have Glanzmann thrombasthenia and Afibrinogenemia
?
Defects of Primary Aggregation
What defect of platelets is related to aspirin and ethanol?
Defects of Release
See slide 14 for other conditions (long list).
What do the platelets lack in individuals with Bernard-Soulier disorder?
Bernard-Soulier platelets syndrome lacks GpIb/V/IX (necessary for proper platelet adhesion) which leads to lack of adhesion and bleeding conditions.
Inherited Disorder
Compare those with homozygous Bernard-Soulier disorder to heterozygous?*
- Heterozygotes have normal to near normal function
- Homozygotes have giant platelets, thrombocytopenia, usually decreased platelet survival. Moderate to severe bleeding disorder. Platelet counts 40 to near normal.
What is the coagulation problem caused by uremia?
Uremia: Increased urea can cause decreased adhesion, aggregation and defective platelet granule release.
How does DIC impact platelet function?
DIC: Fibrin degradation products known to inhibit adhesion and aggregation.