Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
48 Cards in this Set
- Front
- Back
|
what substances do endothelial cells secrete during haemostasis?
|
von Willebrand Factor, prostacyclin, tissue plasminogen activator
|
|
|
t/f... at site of vessel injury, vasodilation occurs
|
false, vasocnstriction occurs to control the initial rate and volume of bleeding
|
|
|
how do circlating platelets adhere to exposed subendothelial matrices?
|
via vWF
|
|
|
what activates prothrombin to thrombin?
|
factor Xa
|
|
|
what does thrombin do?
|
converts fibrinogen to fibrin
|
|
|
what is the half-life of factor VIII?
|
9-18 hours
|
|
|
t/f... vWF is the largest known soluble protein
|
true
|
|
|
which are the vitamin K dependent coagulation factors?
|
factors II, VII, IX and X as well as protein C and protein S
|
|
|
what is the normal lifespan of platelets?
|
7-10 days
|
|
|
t/f... platelets contain a nucleus
|
false
|
|
|
how does lysis of fibrin occur?
|
plasminogen is activated to plasmin by t-PA and cleaves fibrin degradation products
|
|
|
which factor initiates the extrinsic pathway?
|
factor VII
|
|
|
which clotting factors are produced in the liver?
|
factor II, V, VII, IX, X, fibrinogen
|
|
|
where is vWF synthesised?
|
endothelial cells and megakaryocytes
|
|
|
what are the two roles of vWF in clotting?
|
assists in initial adhesion of platelets to damaged endothelium and stabilises factor VIII in the circulation
|
|
|
what is the half life of factor VII?
|
4-6 hours
|
|
|
what is the half-life of prothrombin?
|
72 hours
|
|
|
what is the half life of protein C?
|
12-16 hours
|
|
|
why is there an initial period of potential hypercoaguability when warfarin treatment is begun?
|
the level of protein C falls before levels of factors X, II and IX have fallen
|
|
|
what Factor VIII level do patients with severe haemophilia have?
|
1% or less
|
|
|
what stabilises factor VIII in the circulation?
|
vWF
|
|
|
what is the inheritance of haemophilia?
|
x-linked recessive
|
|
|
what is the inheritance of von Willebrand's disease?
|
autosomal dominant
|
|
|
t/f... factor VIII may be reduced in vWD?
|
true
|
|
|
which of the haemophilias is more common?
|
heamophilia A (4 times as common as haemophilia B)
|
|
|
what does prothrombin time (PT) test?
|
extrinsic pathway i.e. factors II, V, VII, X
|
|
|
what tests the intrinsic pathway?
|
activated partial thromboplastin time (APTT) - tests factors VIII, IX, XI, XII, X
|
|
|
which times will be prolonged with heparin administration?
|
APTT and TT but not PT
|
|
|
are petechiae more common in clotting disorders or platelet dysfunction?
|
platelet dysfunction or thrombocytopenia
|
|
|
what is Lyonisation?
|
skewed X inactivation
|
|
|
what percentage risk does the son of a female carrier of haemophilia have of being affected?
|
50%
|
|
|
what fraction of cases of haemophilia are a result of new mutations?
|
approximately 1/3
|
|
|
t/f... the factor VIII gene is expressed in the bone marrow, lymphocytes and endothelial cells
|
false, it is expressed in the liver, spleen, lymph nodes and other tissues
|
|
|
at what platelet count does spontaneous bleeding occur?
|
<20 x 10^9/L
|
|
|
what do blood vessels release when injured causing vasoconstriction?
|
endothelin
|
|
|
which substances released by endothelium inhibit platelet adhesion?
|
prostacyclin, EDRF (NO), t-PA
|
|
|
what surface is required for coagulation?
|
phospholipid surface (also need calcium and activator e.g. tissue factor)
|
|
|
which coag factor initiates the extrinsic pathway?
|
VII
|
|
|
which coag factor initiates the intrinsic pathway?
|
XII
|
|
|
how does protein C inhibit coagulation?
|
turns off the two cofactors (V and VIII)
|
|
|
where does bleeding due to platelet disorders occur?
|
mucosal surfaces and skin
|
|
|
which type of vWD is autosomal recessive?
|
type III
|
|
|
what fraction of platelets are in the spleen?
|
1/3
|
|
|
why is splenomegaly accompanied by thrombocytopenia?
|
platelets sequestered in the spleen
|
|
|
what percentage of children with acute immune thrombocytopenic purpura will develop chronic immune thrombocytopenic purpura?
|
5-10%
|
|
|
what percentage of Haemophilia A is due to an inversion of gene from intron1-22?
|
50%
|
|
|
how is haemophilia A treated?
|
recombinant factor VIII
|
|
|
why does liver disease cause bleeding problems
|
impaired synthesis of clotting factors, thrombocytopenia, increased fibrinolysis, platelet dysfunction, dysfibrinogenaemia
|
