CARDIO- haemostasis

Question 1

outline the haemostatic pathway

Answer 1

severed blood vessel - blood and blood components are leaking out

vascular spasm - smooth muscle contracts reducing blood loss

platelet plug formation - platelets activated by chemicals released from injury site and by contact with underlying collagen

coagulation - fibrinogen is converted to fibrin - forms a mesh that traps more platelets and erythrocytes forming a clot

Question 2

outline the formation of a platelet plug

Answer 2

platelets become spiked and stick to each other and the wound site

initial platelets are activated by chemicals released from the injured cells and by contact with broken collagen

bound platelets release chemicals that activate and attract other platelets

Question 3

what is a mechanism by which the vascular endothelial cell regulated haemostasis and how is it altered by physical damage

Answer 3

vasoconstriction

infection could cause vasodilation
physical damage causes increased vasoconstriction

Question 4

what are some examples of disorders of clotting

Answer 4

haemophilia - failure to clot due to mutations in coagulation factors

thrombosis - clotting in the wrong places causing stroke / VTE / PE

disseminated intravascular coagulations - whole body clots leading to sepsis and depletion of clotting factors and platelets leading to bleeding

Question 5

describe the role of the clotting system in defence

Answer 5

activation forms a physical barrier - easier for pathogen clearance by immune cells

tissue factor triggers coagulation independent signalling pathways mediated by protease activated receptors on immune cells

protease activated receptors evoke pro and anti - inflammatory pathways that regulate the migration and proliferation of immune cells

containment hypothesis