Platelets and Plasma

Question 1

How big are platelets?

Answer 1

2-5um

Question 2

How long do platelets live?

Answer 2

7-10 days

Question 3

Where do platelets come from? (How are they made)

Answer 3

The megakaryocyte by exocytosis

Question 4

Where are platelets made?

Answer 4

In the bone marrow and then travel in the blood

Question 5

What are platelets role?

Answer 5

• Small cytoplasmic anucleate cells that block up holes in blood vessels
• They clot the blood

Question 6

What controls platelets?

Answer 6

Thrombopoetin

Question 7

What increases the platelet production?

Answer 7

The c-mpl which is the thrombopoetin receptor and it regulates the differentiation of the megakaryocyte

Question 8

What are TPO mimetics?

Answer 8

They are drugs that considerably increase the platelet count as the activate the c-mpl receptor

Question 9

What do platelets contain structurally?

Answer 9

• Plasma membrane
• Cytoskeleton
• Dense tubular system
• Secretory granules (alpha, dense e.g. serotonine, lysosome and peroxisome)

Question 10

What is thrombocytopenia?

Answer 10

A reduced number of platelets which can cause bleeding, most seriously cerebral bleeding. Can be caused by some medications, liver disease or renal failure.

Question 11

What is thrombocytosis?

Answer 11

A high number of platelets: Can lead to arterial & venous thrombosis, leading to an increased risk of heart attack + stroke.

Question 11

What is thrombocytosis?

Answer 11

A high number of platelets: Can lead to arterial & venous thrombosis, leading to an increased risk of heart attack + stroke.

Question 12

What is a common phenotype for a problem with platelet count?

Answer 12

A petechial rash
- Skin, mucosal bleeding or bruising
- Look at sites of high pressure (legs, ankles)

Question 13

What are some pathogenic causes for thrombocytopenia?

Answer 13

• 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)

Question 14

When is a platelet transfusion needed?

Answer 14

• 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

Question 15

What is the process of normal haemostasis? (stopping of blood flow)

Answer 15

• Coagulation cascade: normal procoagulants and anticoagulants (help with controlling blood coagulation)
• Termination
• Fibrinolysis (breakdown of fibre in blood clots)

Question 16

What can go wrong in the normal process of haemostasis?

Answer 16

• Low platelet count so an increased platelet activation
• Low procoagulants and anticoagulants so blood can’t coagulate or coagulates too much

Question 17

What is blood plasma?

Answer 17

The liquid component of blood that holds the cellular elements of whole blood in suspension

Question 18

What is blood serum?

Answer 18

Blood plasma without the clotting factors

Question 19

What does plasma consist of?

Answer 19

• Water (up to 95%)
• Electrolytes
• 02 and CO2
• Proteins (albumin, globulins, hormones, coagulation factors)
• Transport proteins (transferrin, haptoglobin)

Question 20

What is FFP?

Answer 20

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)

Question 21

When should FFP be used and not used?

Answer 21

• Plasma should not be used for volume replacement
• There is a big transfusion protocol to follow