clotting Flashcards
define embolus
object from another part of the body that obstruct the blood flow – most typically a blood clot (thrombus) that becomes an embolus
where are common sites for embolus formation?
brain, heart, lungs
how does a thrombus become an embolus?
it starts to break down and then lodges in other vessels
what does an insoluble clot do?
plugs leak in vascular wall and can occlude vessel
what do healthy vessels secrete to inhibit clot formation?
vasodilators - prostaglandins I2, NO
how do smooth muscles in vessel walls respond to damage?
vasoconstriction
how does damage in vascular wall result in leaking and clotting?
- Damage results in exposure of basement membrane – blood exposed to collagen, subendothelial tissue factor
- Damage causes exposure to vessel wall – blood now exposed to platelet activating factor
- Damage leads to exposure in lysed epithelial cells – blood exposed to ADP (adenosine diphosphate which causes fibrinogen bridge formation)
- Break in bottom of vessel will cause leakage – vessel responds immediately (vasoconstriction)
what happens during vitamin C deficiency?
reduced produced of collagen - decreased clotting
scurvy - excessive bleeding
what does NO and nitrates do?
vasodilation - therapeutic and recreational
how does corticosteroid effect collagen production?
reduced collagen production when in excess
what does ehlers danlos syndrome result in?
genetic defect producing a reduction in collagen production
what is the function of platelets?
secrete factors to activate other platelets (ADP), allow adhesion (vWF), vasoconstriction
early plug to maintain homeostasis
where are platelets produced?
mega carrier site within bone marrow
what do cancers in bone marrow do to cell types?
expansion of some and then squish others - discrepancies indicate pathology
how many pathways are there within clotting factors?
2 (intrinsic and extrinsic) and they converge into one common one
what are key components within the clotting factor cascade?
calcium
- Centres on prothrombin to thrombin which then allows fibrinogen to convert to fibrin which essentially causes the clot by cross linking
why is regulation of coagulation vital?
there is enough clotting potential within 1ml of blood to clot all the fibrinogen in the body in 10 to 15s
what is the role of anti-thrombin?
serpin SERine protease inhibitor (heparin facilitates anti-thrombin action
what is vitamin K deficiency usually seen with?
short bowel syndrome
what is coumains role within VitK deficiency?
- Coumain prevents the reduction of vitamin K epoxides in liver microsomes and induces a state of analogous to vitamin K defiency
what are commonly inherited haemophilias?
mutation in factor V gene and mutation within prothrombin gene
what are fibrin clots degraded by?
serine proteases , plasmin
how does plasmin degrade fibrin clots?
- Plasmin circulates in plasma as inert precursor (zymogen) plasminogen
- Plasminogen is converted to plasmin by two serine proteases – tPa and uPA
- Plasminogen activator inhibitor inhibits tPA causing fibrin to be degraded
name some thrombolytic drugs
streptokinase, tPA, uPA
they promote dissolution of thrombi and activate plasminogen to plasmin
