Clotting

Question 1

define thrombosis

Answer 1

solid mass of blood constituents formed within an intact vascular system

Question 2

what factors predispose to thrombosis

Answer 2

Virchoffs triangle
Blood flow change (laminar→ turbulent) (stasis)

Change in vessel wall (endothelial cell injury) (smoking causes damage)

Hypercoagulable state (inherited) (COCP)

Question 3

define embolus

Answer 3

mass of material in the vascular system able to become lodged within a vessel and block it

Question 4

define ischaemia

Answer 4

reduction in blood flow

Question 5

define infarction

Answer 5

reduction in blood flow leading to cell death

Question 6

what causes infarction

Answer 6

Ischaemia and low O2

Question 7

which organs are supplied by end arteries

Answer 7

kidneys
liver
spleen
lung
brain
retina

Question 8

what are platelets

Answer 8

Platelets are colourless anucleate cell fragments containing granules. They are produced when cytoplasmic portions of large bone marrow cells - megakaryocytes - pinch off and enter circulation

Question 9

overview of how a thrombus forms

Answer 9

1. vwf –> platelt plug
2. Clotting cascade –> fibrin web

Question 10

platelet plug formation

Answer 10

1. vwf is released by endothelial cells and binds to exposed collagen
2. circualting platelets bind to vwf
3. activation and aggregation
4. platelet plug contracts due to myosin and actin within

Question 11

what does VWF do in platelet plug

Answer 11

provides a bridge to collagen and allows platelets to activate

Question 12

what does thromboxane do, platelet plug

Answer 12

stimulates platelets to express TP receptors that allow fibrinogen to bind. also stimulaes vasoconstriction

Question 13

what does ADP do, platelet plug

Answer 13

activates platelets

Question 14

what does fibrinogen do

Answer 14

aggregates platelets

Question 15

what does the liver do which is important for clotting?

Answer 15

produces clotting factors 10, 9,7,2

produces bile salts needed for absorption of vitamin K (needed for production of 10, 9, 7, 2)

Question 16

what is overall role of coagulation proteins

Answer 16

to convert soluble fibrinogen into insoluble fibrin

Question 17

what is the key enzyme in clotting cascade

Answer 17

thrombin (factor 2a) -

catylases convertion of fibrinogen to fibrin

Question 18

what are platelets and proteins activated by?

Answer 18

tissue factor - on cells other than endothelium

Question 19

What is the intrinsic pathway activated by? what factors involved?

Answer 19

The intrinsic pathway is activated by contact with a damaged surface and goes as follows:
Factor XII → Factor XI → Factor IX (+ Factor VIII + vWF) → Common pathway

Question 20

what is the extrinsic pathway activated by? what factors involved?

Answer 20

The extrinsic pathway is activated by the release of tissue factors and goes as follows:
Factor VII → Common pathway

Question 21

what factors are involved in the combined pathway?

Answer 21

The combined pathway then proceeds the intrinsic/extrinsic pathways and goes as follows:
Factor X (+ Factor V) → Factor II → Factor I (+ Factor XIII → Fibrin mesh)