Pathology Circulation

Question 1

Origin of platelets

Answer 1

formed from megakaryocytes in the bone marrow

large cell with many nuclei

undergoes nuclear divisions but not cell divisions so huge cell with many nuclei

Question 2

role of platelets in forming a thrombus in relation to trauma or tissue damage

Answer 2

trauma to vessel - exposure of platelets to interstitial collagen

platelets adhere together to try to form bridge to close gap - become sticky

platelets have molecules on their surfaces which allows adherence to interstitial collagen, even when blood is flowing past them - clotting cascade deposit factor VII enhancing this further

Question 3

main site of production of certain key clotting factors

Answer 3

liver (also epithelial cells)

Question 4

production of fibrin

Answer 4

thrombin converts soluble fibrinogen into insoluble fibrin

fibrin forms a mesh of strands

Question 5

thrombus formation

Answer 5

occurs in flowing blood

pure thrombus is pale cream coloured

thrombus consists of platelets and mesh network of fibrin strands

platelet thrombus when platelets form on edge of blood vessel

Question 6

Clot formation

Answer 6

blood leaks out of the vessel and becomes stationary (or stagnant)

clot consists of a network of fibrin strands and red blood cells

clotting system is activated by collagen and by the stagnant blood formation, forming a clot

vessel vasoconstricts to decrease blood loss

a platelet and fibrin thrombus forms to bridge the gap between the ends of the vessels adjacent to flowing blood

Question 7

what is haemostatis

Answer 7

the stopping of blood flow

Question 8

Granulation tissue

Answer 8

the capillaries that grow in (granulation tissue) can oxygenate the area of the wound and keep it alive

Question 9

How to remove a thrombus

Answer 9

a blood protein called plasminogen converts to plasmin, and plasmin cuts up fibrin into smaller fragments, as a way of removing fibrin

in a thrombus this is sometimes called a thrombolysis

in blood there is a fibrinolytic system which removes fibrin and stops thrombi from propagating

Question 10

blood vessel structure

Answer 10

normal small artery or artery branch

endothelia cell lines lumen

basal lamina surrounds endothelial cells

smooth muscle cells around basal lamina

around smooth muscle cells are interstitial collagen fibres

lumen contains red and white blood cells and platelets