Thrombosis

Question 1

What is a clotting factor?

Answer 1

A group of proteins in the blood

many are produced by the liver or endothelial cells

Question 2

What does factor xa convert prothrombin into?

Answer 2

thrombin

Question 3

what does thrombin then convert fibrinogen into?

Answer 3

fibrin

it’s insoluble - a blood clot

Question 4

define thrombus?

Answer 4

it is a blood clot that occurs within a vein

Question 5

what is a blood clot?

Answer 5

just a coagulation of blood but generally all around the body

Question 6

structure of a typical vein

Answer 6

interstitial collagen fibers surrounding outside
then smooth muscle lining of lumen
then basal lamina (basement membrane)
inside lumen you have plasma which has WBCs, RBCs, and platelets
plasma also contains clotting factors- without these it would be called serum

Question 7

what are the 2 path ways in blood clotting

Answer 7

intrinsic (damaged surface)
extrinsic (trauma- extreme)
these converge to form the common pathway

Question 8

what is the clotting cascade?

Answer 8

an amplification system

Question 9

what could initial damage to a blood vessel be cause by?

Answer 9

trauma- leads to exposure of interstitial collagens or of a molecule called tissue factor

Question 10

what is a tissue factor?

Answer 10

a molecule present on muscle cells and is released by it- once released it can bind a clotting factor and initiate the clotting cascade

Question 11

what are serine proteases?

Answer 11

they have a serine amino acid in them and they cleave other clotting factors to activate them and then they go on to do the same
many clotting factors are serine proteases

Question 12

what does the clotting cascade lead to the production of? and what is the end point?

Answer 12

thrombin

the end point is the production of insoluble fibrin strands that form a meshwork

Question 13

Platelets
what are they?
how do they work?

Answer 13

formed in the bone marrow
they form a cell called megakaryocyte with many nuclei (undergoes nuclear division but not cell division)
platelets bud off as fragments from cytoplasmic extension
they work by trying to close the gap caused by trauma to a vessel which happens when they’re exposed to interstitial collagen

Question 14

what are the 2 types of coagulation?

Answer 14

thrombus formation

blood clot formation

Question 15

thrombus formation (thrombosis)

Answer 15

it occurs in flowing blood as platelets have molecules on their surface which allow adherence to interstitial collagen even when blood is flowing past them
pure thrombus= pale cream colour

it consists of platelets and a mesh like network of fibrin strands

Question 16

clot formation

Answer 16

blood leaks out of a vessel and becomes stationary (or stagnant)
within the stagnant blood, sitting next to the interstitial collagen, the clotting cascade is activated

Question 17

what does a clot consist of

Answer 17

a network of fibrin strands and RBC’s

Question 18

define haemostasis

Answer 18

stopping bleeding

Question 19

what are the new blood vessels that can grow into the area of the wound called?

Answer 19

granulation tissue

Question 20

the capillaries that grow in granulation tissue can help do what in the wound?

Answer 20

oxygenate it and keep it alive

Question 21

what could potentially go wrong with thrombosis

Answer 21

if it blocks off vessel as this leads to ischaemia (leak of blood flow to tissue) or hypoxia (lack of O2 in tissues)

if it causes stagnant blood to build up behind the thrombus and block blood flow through the vessel

Question 22

how is excess thrombus/clot removed

Answer 22

fibrinolytic system- removes fibrin and stops thrombi from propagating
plasmin cuts up fibrin into fibrin degradation products

Question 23

what does the fibrinolytic system depend on?

Answer 23

plasma protein called plasminogen being converted to plasmin

Question 24

3 things associated with abnormal thrombosis and clotting are called what?

Answer 24

virchow’s triad

abnormalities of vessel wall, constituents of the blood, blood flow