Blood coagulation, homeostasis and its investigation

Question 1

what is the purpose of von Willibran factor?

Answer 1

platelet adhesion

Question 2

give a brief overview of the main phases of homeostatsis

Answer 2

primary homeostasis - vasoconstriction + platelet adhesion, aggregation and contraction

secondary homeostasis - coagulation factor activation and fibrin formation

fibrinolysis - fibrinolysis activation and lysis of platelet plug

Question 3

what is the purpose of prothrombin?

Answer 3

small quantity of prothrombin forms thrombin (activated form) –> activates platelets and other coagulation factors –> activated platelets bind more factors –> thrombin burst –> then activates fibrinogen to form fibrin –> fibrin forms mesh over platelet plug –> stabilising clot

Question 4

what is D-dimer testing and what does a positive result indicate?

Answer 4

testing for the presence of fibrin degradation products called D-dimers.
positive result indicated excessive fibrinolysis.

Question 5

what is thrombin time and what aspect of the coagulation cascade is it sensitive to?

Answer 5

time taken for clot to form.

it’s sensitive to fibrin formation from its inactive precursor fibrinogen

Question 6

what aspect of the coagulation cascade is prothrombin time sensitive to?

Answer 6

extrinsic pathway (tissue factor dependent pathway)

Question 7

what aspect of the coagulation cascade is APTT sensitive to?

Answer 7

intrinsic pathway

Question 8

what can mixing studies tell us about a patient’s blood?

Answer 8

a mixing study with normal APTT after 50:50 mix indicates a deficiency in the patient’s blood.
a mixing study with abnormal APTT after 50:50 mix indicates the presence of an inhibitor in the patient’s blood e.g. warfarin