Physiology Homeostasis and CLOT LYSIS

Question 1

what is haemostasis (1)

Answer 1

process to prevent and stop bleeding

Question 2

what are the stages in haemostasis ?

6

Answer 2

1) vasospasm to reduce blood flow 
vasoconstriction occurs due to :
->endothelin ( secreted From endothelium )
->sympathetic innervation 
->myogenic spasm 

2) Temporary platelet plug formation:
- >COLLAGEN is exposed this means that the platlets can attach to the site easily with help from von willebrand factors (VWF)
- >platlets release platelet factors such as :ABP (adenosine Bisphospate = increases platelet aggregation,Prothrombin A2/Thromboxane A2 =increases platelet aggregation and vasoconstriction , Serotonin which also increases vasoconstriction

3) Clotting and coagulation to form FIBRIN plug
- both intrinsic and extrinsic pathways lead to FACTOR 10 -
- factor 10 becomes activated and produces a prothrombin activator called prothrombinase
- prothrombin—>thrombin
- thrombin +ca2+ —>converts fibrinogen —>fibrin making a stable fibrin mesh .

Question 3

what is the intrinsic coagulation pathway

3

Answer 3

everything occurs within Blood vessel

1) vessel rupture , collagen is exposed
2) platlets are activated and release clotting factors , which all activate one after the other
3) eventually lotting factor 10 is made after a cascade–>common pathway

Question 4

what is the extrinsic coagulation pathway

3

Answer 4

1-tissue factor is released from OUTSIDE the Blood vessel wall
2-Tissue factor+factor 7= complex
3-meets at the common pathway at factor 10
VERY QUICK , LESS REACTIONS AND RAPID ACCELERATION TO FACTOR 10

Question 5

what is the COMMON coagulation pathway

3

Answer 5

1-FACTOR 10 ACTIVATED –>prothrombin activator called prothrombinase
2-Prothrombin –>thrombin
3-thrombin +ca2+ –>converts fibrinogen to fibrin and factor 13 helps to stabilise the plug

Question 6

Fibrinolysis explaination

2

Answer 6

1-Fibrin specific plasminogen activator turns plasminogen —–>Plasmin (protease which breaks down clot)
phagocytes clear up debris

Question 7

distinguish between bleeding and clotting time

Answer 7

1)bleeding time = phase 1/2= normal 3-4 minutes .
Variation can indicate platelet disease

2)Clotting time = measure of thrombin synthesis = 10 min = deflects indicate problem with phase 3 coagulation

Question 8

what is the role of thrombin ?(4)

Answer 8

1-Causes platelet aggregation
2-Causes fibrinogen –>fibrin
3-enhances production of more prothrombin
4-activates factor 13 which tightens fibrin clot

anticoagulants take thrombin out of blood preventing formation of blood clot