Unit 2 - blood vessels/ haemostasis Flashcards
what are the three layers of blood vessel wall
tunica intima
tunica media
tunica adventitia
what consists the tunica intima?
endothelium subendothelium (collagen) internal elastic lamina
what is the function of the tunica media?
provides structural support (smooth muscle fibres - arranged in lamellae) and vasoreactivity (vasoconstriction/dilation)
what is the difference in the thickness of tunica media in arteries and veins?
thicker in arteries
what components are found in the tunica adventitia?
fibroblasts
vaso vasorum - nutrients/ remove waste from wall
nervi vasorum - regulate vasoreactivity
where does atherosclerosis have its effect?
plaque between tunica intima and media
- contains foam cells and smooth muscle cells
how does scurvy affect blood vessels?
production of structural faulty collagen - loss of vessel integrity
what proteins are found in blood?
haemostatic proteins = coagulation factors/ fibrinolytic system/ regulatory
transport: specific/ non-specific
give example of specific transport proteins
lipoproteins
VLDL/ LDL - atherogenic
HDL - anti-atherogenic
give example of non-specific transport protein
albumin
what clinical tests are used to analyse liquid component of blood?
coagulation screen/ BMP (basic metabolic panel)/ cholesterol test
what is the first step of haemostasis?
vessel constriction - damaged endothelium - localised contractile response of smooth muscle causes narrowing of blood vessels:
decreased blood flow/ increased shear force/ decreased blood volume
what is the first stage of clot formation?
primary haemostasis
- loss of endothelial cells exposes collagen in subendothelium so von Willebrand factor binds directly
- conformational change in VWF allows it to bind to platelets to begin formation of soft clot
- platelets also bind to the collagen directly using platelet glycoprotein receptors
- platelet activation: change of shape/ release of molecules/ surface negatively charged
explain the intrinsic pathway
XIIa →XIa →IXa.VIIIa→X→Xa.Va→IIa (→fibrinogen to fibrin)
explain the extrinsic pathway
TFVIIa→X→Xa.Va→IIa (→fibrinogen to fibrin)
what is the common pathway?
Xa.Va→IIa (→fibrinogen to fibrin)
what is coagulator factor II and IIa known as?
prothrombin and thrombin
fibrin polymers are cross connected to the clot by?
FXIIIa
what is the classical model of fibrin formation?
intrinsic/ extrinsic pathway
what are three components to the cell-based model?
initiation
amplification
propagation
describe initiation
small amounts of coagulation factors diffuse from vasculature into surrounding tissues and become non-specifically activated
= similar to extrinsic pathway (apart from Va)
TFVIIa→Xa→IIa
describe amplification
coagulation factors from blood come into contact with thrombin produced which is a potent activator leading to activation of platelets and substrate coagulation factors (Va/ VIIIa/ XIa)
describe propagation
formation of IXa.VIIIa complex which has high affinity for negatively charged platelets
- similar to intrinsic pathway to produce more thrombin -thrombin burst(IXa.VIIIa→X→Xa.Va→IIa (→fibrinogen to fibrin)
complexes bind to phospholipid surface are adjacent to each other - efficient process
what is the three types of haemophilia?
A - factor XIII deficiency
B - factor IX deficiency
C -factor XI deficiency
(activity of IXa.VIIIa complex compromised - inefficient fibrin formation)
give 3 tests of haemostasis
APTT - activated partial thromboplastin time (time of intrinsic pathway)
PT - prothrombin time (time of extrinsic pathway)
fibrinogen/ claus assay - how much fibrinogen present
what is INR?
international normalised ratio - monitors anticoagulant therapy for patients with thrombosis treated with warfarin
what is the clinical presentation of a patient with haemophilia A?
subcutaneous haematoma
what is the clinical presentation of a patient with haemophilia B?
joint bleed in knee (ankles)
what is the effect of DVT?
deep vein thrombosis - thrombus impairs blood flow - oedema/ phlebitis
