Case 1 Independent Learning Flashcards
What are the layers of a vessel wall from inside to outside
Tunica intima, subendothelium, internal elastic lamina, tunica media and tunica adventitia
Describe tunica intima
Also known as endothelum. Composed of endothelium cells and is a continuous membrane
Describe subendothelium
Composed of fibrous collagen which means the blood vessel retains its shape during contraction and expansion
Describe internal elastic lamina
Composed of elastin fibres which means the blood vessel retains its shape during contraction and expansion
Describe tunic media
Composed of smooth muscle fibres, elastin and collagen is fed by the autonomic nervous system which stimulates vasoconstriction or vasodilation
Describe tunica adventitia
Composed of collagen, fibroblasts and elastin which provide support and shape the vessel around the surrounding tissue
What is formed in primary haemostasis
A soft clot involving platelets and von willebrand factor. The soft clot heals the sight of damage however is not strong or stable enough on its own
What happens during secondary haemostasis
The clot is stabilised by fibrin which goes over and through the clot
During primary haemostasis what sticks platelets to the wall of the vessel
von Willebrand factor
What happens when the vessel wall is damaged
Collagen of the subendothelium is exposed resulting in von Willebrand factor changing shape which causes platelets to bind
What happens when platelets bind to the damaged vessel wall
They activate other platelets via platelet aggregation resulting in the formation of a soft clot
What is factor II called when inactive and then when active
II= prothrombin IIa= thrombin
What is factor III called and where does is come from
Tissue factor which comes from outside the blood
What is factor I called when inactive and then when active
I= fibringogen, Ia= fibrin
Where does the the common pathway start
At X being converted to Xa.Va
What is Xa.Va called
Prothrombinase complex
What are the three stages of the current model
Initiation, amplification and propagation
What happens in initiation
Coagulation occurs as surrounding tissue is activated and combines with tissue factor
What happens in amplification
Vessel damage results in primary haemostasis and thrombin activated incoming coagulation factors
What happens in propagation
The negative platelet surface attracts coagulation factors which bind to platelets which results in large amounts of thrombin being produces which is a called a ‘trombin burst’ and results in fibrization
What are the 3 aspects of the classic model
Intrinsic pathway (starts factor XII), extrinsic pathway (starts and factor III) and common pathway (starts at factor X)
What do people with haemophilia A lack
Factor VIIIa
What do people with haemophilia B lack
Factor IXa
Which model explains why haemophiliacs bleed
Only the current model (not the classic)