Lect 4 - Haemostasis Flashcards
Coagulation is the process that results in the generation of
Thrombin
Thrombin converts what into what
Soluble fibrinogen to insoluble fibrin
Fibrin along with __ is needed to do what?
Platelets
Arrest bleeding
When coagulation pathways are activated, fibrinolysis is also. What is fibrinolysis?
The process of breakdown of fibrin
Platelets adhered to exposed subendothelial collagen fibres cause a “release action” of platelet constituents such as [4]
ADP
Serotonin
Epinephrine
Histamine
Endothelium, particularly of the pulmonary micro-circulation actively removes substances from the circulation that promote platelet aggregation such as
Prostaglandin F1 Serotonin Adenine nucleotides Bradykinin Angiotensin-1
Also, all layers of blood vessels, but especially the endothelium and the intima synthesize and release [1] potent inhibitor of platelet aggregation and promotor of vasodilation
Prostacyclin (Prostaglandin I2)
The endothelial surface is protected from thrombresistance by a carbohydrate rich cell coat called
Gylcocalyx
The endothelium produces __, a potent vasodilator which also inhibits platelet adhesion and aggregation
Nitric oxide
What are platelets? Where do they come from?
Anucleate cytoplasmic pieces shed from megakaryocytes mainly in the bone marrow. Lungs and Spleen are also sources of platelets.
They are the smallest formed elements in stained blood smears stained with what stain
Romanowsky
Circulating platelets in mammals vs non mammals
Mammals - Discoid and anucleated
Non mammals - have nuclei
How do equine platelets appear under a stain
Faint and may be difficult to see
Platelets can synthesize certain lipids, which are needed for the formation
AA > Prostaglandin PGH2 via COX > TxA2
The lifespan of the platelet is
5-10days
Platelet production is regulated by
Thrombopoietin
Platelets adhere to exposed sub-endothelial collagen, mostly via what bond
von Willebrand factor
von Willebrand factor bonds to the platelet receptor ___
Glycoprotein 1b
vWF is a protein formed by what? [2] and found where [2]
Endothelial cells and megakaryocytes
Platelets and plasma
After adhesion to the site of vascular injury, platelets adhere to each other via bind to fibrinogen and vWF interacting with certain platelet surface receptors, rapidly enlarging the platelet plug. Fibrinogen interacts with these surface receptors [2]
IIB and IIIA
Aggregating platelets release [2] which promotes further platelet adherence. They also begin synthesizing [1] a prostaglandin that causes irreversible platelet aggregation and intense local vasoconstriction. The platelet plug formed at this point is unstable and is called the [1]. The process by which it is formed is called [1]
ADP and Fibrinogen
TxA2
Primary hemostatic plug
Primary haemostasis
When platelets are activated, certain phospholipids collectively called [1], move from the inner to outer membrane of the platelet, and are available for use as cofactors in the coagulation pathway
Platelet factor 3
[1] (formed during the process of coagulation) stimulates [1] formation with the primary platelet plug. This, along with the platelet contractile mechanism, result in formation of a [1] (secondary haemostatic plug– this is called [1]
Thrombin
Fibrin
A stable plug
Secondary haemostasis
Aspirin is an effective inhibitor of the platelet release reaction by acetylating COX I and inhibiting TxA2 production except in what species
Bovine
Fibrinolysis is achieved by the fibrinolytic enzyme
Plasmin
The action of plasmin on fibrin or fibrinogen results in the formation of
FDP (Fibrin degradation products)
Plasmin generation is strongly inhibited in plasma by substances called
Antiplasmins
Anti-thrombin III (AT III) which accounts for 80% of the naturally occurring plasma inhibitory activity. The anti-coagulation activity of AT III is greatly enhanced by [1], particularly against factor [2]
Heparin
Xa and thrombin
Antithrombin III is synthesized where
Liver
These [2] vitamin K dependant factors destroy Va and VIIIa
Protein C and S
Platelet clumping/aggregation leading to pseudothrombocytpenia occurs frequently and is most commonly seen in what species
Cats
This species has platelets of variable size which can be as large as an RBC
Feline
EDTA- induced clumping has occasionally been reported in what species
Horse
Which breed of dog have natural lower platelet count
Greyhounds
Anaplasma platys infection (infects platelets and causes what in dogs
Cyclic thrombocytopenia
The most inherited bleeding disorder in dogs but rare in cattle, cats and horses
vWD
What breed of dog is highly affected by vWD
Doberman pinchers
The Bernard - Soulier Syndrome is
Abnormality or a deficiency of platelet glycoprotein 1b. Affected animals exhibit mild to moderate bleeding. Bleeding time (BMBT) is prolonged but clot retraction is normal.
