Platelets and Plasma Flashcards
How big are platelets?
2-5um
How long do platelets live?
7-10 days
Where do platelets come from? (How are they made)
The megakaryocyte by exocytosis
Where are platelets made?
In the bone marrow and then travel in the blood
What are platelets role?
- Small cytoplasmic anucleate cells that block up holes in blood vessels
- They clot the blood
What controls platelets?
Thrombopoetin
What increases the platelet production?
The c-mpl which is the thrombopoetin receptor and it regulates the differentiation of the megakaryocyte
What are TPO mimetics?
They are drugs that considerably increase the platelet count as the activate the c-mpl receptor
What do platelets contain structurally?
- Plasma membrane
- Cytoskeleton
- Dense tubular system
- Secretory granules (alpha, dense e.g. serotonine, lysosome and peroxisome)
What is thrombocytopenia?
A reduced number of platelets which can cause bleeding, most seriously cerebral bleeding. Can be caused by some medications, liver disease or renal failure.
What is thrombocytosis?
A high number of platelets: Can lead to arterial & venous thrombosis, leading to an increased risk of heart attack + stroke.
What is thrombocytosis?
A high number of platelets: Can lead to arterial & venous thrombosis, leading to an increased risk of heart attack + stroke.
What is a common phenotype for a problem with platelet count?
A petechial rash
- Skin, mucosal bleeding or bruising
- Look at sites of high pressure (legs, ankles)
What are some pathogenic causes for thrombocytopenia?
- Reduced production (reduced megakaryocytes)
- Increased destruction
- Altered redistribution (large spleen means platelets are destroyed early can cause problems)
- Congenital (E.g. Bernard-Soulier Syndrome - big blood platelets so low platelet count and bleeding tendency)
- Acquired (medication related or an underlying disease)
When is a platelet transfusion needed?
- There is a cut off and if they are too low then they will be required a platelet transfusion.
- Normally if it is below 10 (1 x 10^9), then a transfusion is needed
What is the process of normal haemostasis? (stopping of blood flow)
- Coagulation cascade: normal procoagulants and anticoagulants (help with controlling blood coagulation)
- Termination
- Fibrinolysis (breakdown of fibre in blood clots)
What can go wrong in the normal process of haemostasis?
- Low platelet count so an increased platelet activation
- Low procoagulants and anticoagulants so blood can’t coagulate or coagulates too much
What is blood plasma?
The liquid component of blood that holds the cellular elements of whole blood in suspension
What is blood serum?
Blood plasma without the clotting factors
What does plasma consist of?
- Water (up to 95%)
- Electrolytes
- 02 and CO2
- Proteins (albumin, globulins, hormones, coagulation factors)
- Transport proteins (transferrin, haptoglobin)
What is FFP?
Fresh Frozen plasma
- plasma transfusion
- Standard coagulation tests need to be done on patients and a detailed family bleeding history
- the risk is disease transmission or anaphylactoid reaction (same reaction as anaphylactic but different in immune response)
When should FFP be used and not used?
- Plasma should not be used for volume replacement
- There is a big transfusion protocol to follow
