Blood And Blood Groups- Applied

Question 1

Outline the mechanism of blood clotting, identifying the intrinsic and extrinsic pathways

Answer 1

Extrinsic- rapid (within seconds) following tissue damage. Damaged tissues releases a complex of chemicals called thromboplastin or tissue factor which initiates coagulation.

Intrinsic- slower (3-6mins) triggered when blood comes into contact with damaged blood vessel lining (endothelium)

Prothrombin activates the enzyme thrombin, which converts inactive fibrinogen to insoluble threads of fibrin.
As clotting proceeds, the platelet plug is progressively stabilised by increases amounts of fibrin.
After I’ve the clot shrinks because the actin fibres in the platelets contract, squeezing out serum. Clot retraction pulls the edges of the damaged vessel together, reducing blood loss and closing off the hole in the vessel wall.

Question 2

Outline the three stages of Haemostasis

Answer 2

Haemostasis: the normal response of the vessel to injury by forming a clot that serves to limit haemorrhage.
1) vasoconstriction (primary haemostasis)
2) platelet plug formation
3) clot formation (secondary haemostasis)

Question 3

Identify the role of the following in haemostasis: calcium, vitamin K, fibrin and prothrombin activator

Answer 3

Clotting factors are mainly enzymes, they are produced in the liver and circulate as inactive forms in the blood stream. During the clotting cascade they activate each other in a specific order, eventually resulting in the formation of prothrombin activator.

-Prothrombin activates the enzyme thrombin, which converts inactive fibrinogen to insoluble thread of fibrin.
-As clotting proceeds, the plate;t plug is tuba;used by increasing the amounts of fibrin
-Calcium in needed to activated tease, which converts prothrombin to thrombin
-Calcium and Vitamin K are needed to synthesise protein C, an anticoagulant that prevents excessive coagulation after the coagulation cascade occurs.
-Vitamin K is involved in the synthesise of many factors of the coagulation cascade

Deficiency if any of these clotting factors will cause an impaired ability for blood to coagulate, which can contribute to excessive bleeding and haemorrhage