Haemostasis + Anticoagulants Flashcards
what is haemostasis
maintenance of blood in a fluid state when in circulation, clotting blood at the site of injury, removal of the plug when healing is complete
what are thrombi
blood clots
what is thrombopietin
regulates platelet production - produced in the liver and kidneys
from what is a platelet derived?
a megakaryocyte which is derived from the haemopoietic stem cell
how many platelets may be formed from one single megakaryocyte
between 1000-5000
what is primary haemostasis
the formation of a platelet plug
what do glycoproteins do in terms of helping platelets?
they help with platelet aggregation (binding to the membrane surface)
what are the three phases of platelet function
adhesion, activation, aggregation
what are the 13 plasma protein “coagulation factors”
they are inert pro enzymes which become activated during haemostasis
what does factor 1 involve
fibrinogen which helps with clotting
what does factor 2 and 2a include
prothrombin and thrombin
what does factor 3 involve?
calcium
how does factor 4 help with the physiologic cascade
it binds to factor 7
what is another name for factor 8?
anti-haemophiliac A factor
what’s another name for factor nine?
anti-haemophiliac B factor or Christmas factorw
what is the function of factor 13
it is the fibrin stabilising factor
what does vWF stand for
von Willebrands Factor
how do some anticoagulants work with respect to calcium?
calcium is necessary for blood to clot, so many anticoags take calcium out of the blood i.e EDTA
write a note on EDTA
powder anticoag, sodium and potassium salts coat the inside of the blood tube, chelates Ca2+ from the blood, preserves morphology of blood cells for 24-36hrs, may be used in blood counts, may not be used in haemostatic or coagulation studies
write a note on tri-sodium citrate
binds calcium, used in tests for blood function, liquid anticoag, two different conc versions of this anticoag is used. For coagulation tests ratio of 9:1 used, whereas for erythrocyte sedimentation rate test (ESR) 4:1. not suitable for cell counting
write a note on heparin
natural anticoagulant, given to patients who are on Warfarin. Lithium heparin is used in clinical chem assays to measure liver + cardiac enzymes and cholesterol hormones and may be used for cytogenetic tests. inhibits normal coagulation by inactivating factor Xa and iia. not suitable for blood counts and coagulation factor studies.
What components are the involved in haemostatic mechanism
Blood vessels, Platelets, Plasma coagulation factors
What other components ensure that excessive thrombi are not formed?
Natural anticoagulants and Fibrinolytic system
Where are platelets formed?
In the bone marrow by fragmentation of the cytoplasm of megakaryocytes
What happens in Thrombopoieisis
The precursor of Megakaryocyte, the Megakaryoblast arises from differentiation from the haemopoietic stem cell and colony forming unit CFU-GEMM
What is the time interval from differentiation of human stem cell to production of platelets
10 days
Where are procoagulant and anticoagulant factors stored?
within platelet granules and are released into the microenvironment
What is thromboxane A2?
A powerful vasoconstrictor that platelets contain.
What is platelet adhesion?
Where platelets adhere to collagen fibres at the site of injury
What is platelet activation
The change in platelet shape activates the platelet and causes the release of procoagulant molecules which provide a surface for the reactions of the coagulation factors.
What is platelet aggregation?
The primary reversible aggregation and secondary irreversible aggregation that lead to the formation of the primary haemostatic platelet plug.
How does aspirin work?
Reduces the level of platelet aggregation.
What is the purpose of an anticoagulant?
To prevent blood from clotting - inhibits the naction of coagulation system factors
What ion is essential for blood to clot?
Calcium
