Platelet Disorders

Question 1

purpose of hemostasis

Answer 1

stop blood flow from injured vessels

Question 2

thrombocytes prodocution

Answer 2

red bone marrow –> megakaryocytes –> fragmentation –> platelets

Question 3

thrombopoeitin

Answer 3

secreted by liver and kidney to stimulate bone marrow to increase platelet production

Question 4

coagulation factors

Answer 4

produced in liver; circulate in active form –> cut = cascade that activates them in sequential way
vit K and Ca2+ important

Question 5

role of endothelium in hemostasis

Answer 5

helps prevent and control blood clots

1. inhibits coagualtion process normally (PGI2 and NO –> stop activated platelets from sticking to uninjured portions of vessel wall)
2. when damaged –> synthesizes vW factor (role in platelet adhesion and clotting)

Question 6

stages of hemostasis

Answer 6

1. vasoconstriction
2. formation of platelet plug
3. blood coagulation
4. clot retraction and dissolution

Question 7

1. vasoconstriction

Answer 7

vessel spasm –> temporary reduction in blood flow

Question 8

2. formation of platelet plug

Answer 8

1. TXA2 - produced by activated platelets during hemostasis (stimulates activation of platelets and platelet aggregation)
2. vW factor - released by damaged epithelial cells –> platelet adhesion

Question 9

3. blood coagulation

Answer 9

factor x: prothrombin –> thrombin

thrombin: fibrinogen –> fibrin

fibrin (strands of protein subunits, go across plug to trap platelets and RBCs)

Question 10

BC: intrinsic pathway

Answer 10

activated by exposed collagen

longer; more thrombin produced

Question 11

BC: extrinsic pathway

Answer 11

activated by tissue factor released by e. cells

quicker; less thrombin produced

Question 12

4. clot retraction and dissolution

Answer 12

thrombin : stimulates plasminogen activators

plasminogen activators: plasminogen to plasmin

plasmin = protease that breaks down fibrin (dissolves clot)

Question 13

effect of ASA

Answer 13

inhibits cyclooxygenase –> reduced PG and TXA2

reduced TXA2 = less platelet aggregation

Question 14

warfarin

Answer 14

pill

inhibits vitamin K dependent cofactors in both pathways –> less factor X –> less thrombin

Question 15

heparin

Answer 15

IV

acting directly on prothrombin activator (blocking production of thrombin)

Question 16

tissue plasminogen activators

Answer 16

TPA: activates plasminogen –> plasmin

plasmin breaks up fibrin strands (busts clots)

Question 17

thrombocytopenia

Answer 17

decreased platelet levels

1. decreased production due to impaired bone marrow function (aplastic anemia, cancer treatment)
2. viral infections in children
3. transient (2 significant cuts in a row)

Question 18

thrombocytopathia

Answer 18

impaired platelet function

1. inherited (vW disease)
2. acquired (prolonged ASA and NSAID use –> interferes with TXA2 production –> less platelet aggregation)

Question 19

indications of platelet disorders

Answer 19

persistent bleeding from gums or nose

cuts bleed longer than normal

petechiae

easily bruised

blood in feces or vomit

anemia

low BP, fast HR, faint