platelets

Question 1

what are four key roles of platelets

Answer 1

1. primary haemostasis
2. wound healing
3. inflammation
4. angiogenesis

Question 2

describe the development of platelets

Answer 2

in bone marrow, stem cells -> megakaryoblast -> megakaryocytes

• located next to BVs in bone marrow
• once DNA replication finished, granules & membranes form
• pro-platelet extend into capillaries, pro-platelets budd off
• convert to pre-platelets –> platelets

Question 3

what is the most important regulatory factor

Answer 3

thrombopoietin = TPO

Question 4

what are the four aspects of primary haemostasis

Answer 4

1. injury
2. initiation
3. extension
4. stabilisation

Question 5

describe each stage of primary haemostasis

Answer 5

injury
- endothelial damage => vascular constriction

initiation

• von willebrand factor in blood binds to exposed collagen
• VWB factor binds platelets via platelet receptor (GP 1B-IX-V)

extension

• platelet activated -> exposes integrin -> proteins link between platelets (e.g. fibrinogen)
• granules released recruiting more platelets

stabilisation
- using clotting cascade, forming fibrin

Question 6

platelet aggregation pathway

Answer 6

1. adherence to collagen
2. activation of PG synthesis
3. thromboxane A2 released
4. triggered release of platelet granules
   
   • ADP, fibrinogen
5. aggregation

Question 7

thromboxane A2

Answer 7

• phospholipase releases AA from platelet membrane
• COX and thromboxane synthase form

it decreased platelet cAMP -> lowers Ca2+ and causes granule release

Question 8

causes of low platelets

Answer 8

decreased production

• viral infection
• drugs
• marrow failure

increased destruction

• immune thrombocytopenia
• DIC

Question 9

cause of high platelets

Answer 9

increased production

- myeloproliferative neoplasms

Question 10

define immune thrombocytopenia

Answer 10

body produces autoantibodies

• against platelets, destruction by phagocytosis
• against megakaryocytic reducing production

Question 11

treatment for immune thrombocytopenia

Answer 11

prednisone = immune suppression steroid

splenectomy = removes organ of platelet destruction

TPO mimetic = stimulates platelet production