Lecture 8 - Platelets in Health and Disease

Question 1

Platelet development?

Answer 1

Megakaryoblast -> megakaryocyte - more cytoplasm progressively w nuclear development, first DNA replication, then granules and membrane formation

Question 2

Platelet location and effect?

Answer 2

next to blood marrow endothelail cells for releas purposes, releases 4,000 platelets per megakaryocyte

Question 3

Chemical advancing platelet development?

Answer 3

stem cell factor initially, then leukaemia inhibiting factor, and then thrombopoietin (also interleukins)

Question 4

Platelet homeostasis?

Answer 4

constant level, 10% turnover daily, 7-10 day lifespan

Question 5

Platelet key components?

Answer 5

plasma membrane, alpha and electorn-dense granules, mitochondria, glycogen

Question 6

Primary haemostasis?

Answer 6

vascular constriction, platelets aggregate, free Van Willebrand factor binds to exposed collagen of ineffective endothelium, GP-1B-V-IX of platelet binds to form platelet plug, platelets are then activated and integrin alpha-II-beta-Beta-III protein is exposed through membrane changes, also granules are released to recruit and form coagulation cascade

Question 7

Integrin aplha-II-beta-Beta-III second function?

Answer 7

connects platelets to each other via fibrinogen, supported by prostaglandins and Thromboxane A2

Question 8

Platelet cAMP?

Answer 8

acts to keep granules within platelet, Thromboxane A2 decreases (increasing release) and Prostacyclin increases

Question 9

Aspirin function?

Answer 9

decrease thromboxane A2

Question 10

Quiescence?

Answer 10

NO and prostaglandin release from endothelial cells prevent platelet activation through PKA and PKG

Question 11

Causes of altered platelet production?

Answer 11

myeloproliferative neoplasms (increase); viral infection, drugs, bone marrow failure (decrease)

Question 12

Disease affecting platelet destruction?

Answer 12

immune thrombocytoenia/ITP and DIC (increase)

Question 13

Thrombocytopenia - decreased production?

Answer 13

viral, drugs, bone marrow failure (aplasia, leukemia)

Question 14

Thrombocytopenia - increased destruction?

Answer 14

ITB, other autoimmune, drugs, DIC, viral infection

Question 15

Thrombocytopenia - other causes?

Answer 15

hypersplenism, massive transfusion

Question 16

ITB histology?

Answer 16

few but large platelets due to antiplatelet antibodies binding to macrophages via Fc receptor

Question 17

Platelet function defect?

Answer 17

myelodysplasia

Question 18

Hereditary platelet defect?

Answer 18

Glanzmann’s thrombasthesthenia (rare), secretory defects (common) and minor receptor defects (more common)