Coagulation of blood mechanism and its 2 pathways

1. Blood clotting mechanism.
Clotting factors.
Intrinsic and extrinsic pathways.
Anticoagulants.

2. • Clotting or coagulation of blood- conversion of
the fluid part of the blood to a thick jelly, known
as clot or thrombus
• During injuries or wounds
• Solid clot seals up the broken tips of blood vessels
and prevents further bleeding and loss of blood
• Clotting of blood is a major chemical defence
against blood loss
• Serum- straw coloured liquid that oozes out from
the clot – blood plasma without its clotting
factors

3. Blood clotting mechanism:

5. Clotting factors:
• Clotting or coagulation factors - Blood clotting
involves a large number of biochemical agents
• 12 plasma coagulation factors
• 4 platelet coagulation factors
• 1 tissue coagulation factor – it is a plasma
factor
• Coagulation of blood is the net result of a
complex series of enzymatic reactions
• Three major steps

7. Stage I
Stage II
Stage III

8. Plasma coagulation factors:

11. • Enzymecascadesystem
Intrinsic:
• Thromboplastinogen from damaged tissue
cells
Extrinsic:
• Tromboplastinogen from blood platelets
Intrinsic and extrinsic pathways:

13. Anticoagulants:

16. • Warfarin: inhibits the production of vitK
dependent procoagulants
• Use Only in vivo

17. In vitro:
• Oxalates
• Citrates
• EDTA
• Thrombolytics:
• tPA (alteplase)
• Streptokinases

18. Blood transfusion (safety and security
problems):
• Blood transfusion
• Autologus transfusion
• Precautions- blood must be compatible (as ABO,
Rh system), must not contain any communicable
diseases, volume overload and metabolic effects
do not develop
• Blood typing – ABO Rh
• Cross matching- RBC + serum (of both) to check
mismatching if any.
• Importance of Rh –ve blood

20. Hazards of transfusion:
• Acute haemolytic hazards- agglutination of RBC-
haemolysis
Symptoms - chill-rigor-fever-fall of BP, chest pain
(due to blocking of vital artery by clumped RBCs),
jaundice
• Hazards not due to haemolysis: by destruction of
WBCs by the anti-leucocyte/anti-HLA antibodies
Symptom- chill-rigor

22. Hazards due to other causes:
• Excessive transfusion- leading to circultory overload
• Bacterial contamination- restarting of transfusion from the
same bottle
• Metabolic effects due to storing-
Stored blood Hb behaves as fetal Hb, great affinity to O2
and does not easily release O2 – leads to hypoxia
Due to storage of blood in cold environment- hyperkalemia
of plasma of patient- cardiac arrhythmia- death
• Infections- if donor’s blood is not screened properly,
diseases can develop (AIDS, viral hepatitis etc.)

24. • HDN- Haemolytic Disease of the Newborn
• Another variety of Rh incompatibility
• Rh +ve blood in Rh –ve person
• May be during pregnancy

26. Regulation of blood pressure: