| 3 stages of haemostasis: | 1. Vascular spasm
- Damaged blood vessels will constrict to reduce blood flow to the damaged area.
2. Plate plug formation
- Platelet bind to the walls of damaged vessels forming platelet plug and stopping bleeding.
3. Coagulation
- Formation of a stable clot by converting fibrinogen to fibrin |
| The process of Coagulation
involves series of proteins known
as __
These circulate through the
bloodstream as Zymogens and
are activated upon
(1) blood vessel damage or
(2) tissue damage | clotting factors |
| 1 (Blood vessel damage) Damage to the endothelium of the blood vessels leads to the __ pathway
2 (Tissue damage) Trauma to extravascular cells will
trigger the __ pathway. | 1 intrinsic
2 extrinsic |
| Intrinsic pathway process | - The longer pathway and initiated by factor XII (a zymogen) into factor XIIa (an activated protease.
Moreover, this is done upon the exposure to endothelial collagen.
- Then factor XIIa will then activate factor XI to factor XIa.
- Then factor XIa will then activate factor IX to factor IXa.
- Then together with the factor IXa is the cofactor VIIIa which will activate factor X to factor Xa.
- From there on, the common pathway begins. |
| Extrinsic pathway | - Shorter and is initiated upon the release of Tissue factor, which is also known as factor III. It is
released usually from tissue damage.
- Tissue factor (factor III), will activate factor VII to factor VIIa.
- Then factor VIIa in complex with factor III activates factor X to factor Xa.
- From there on, the common pathway begins. |
| The conversion of factor X to factor Xa is done so by the
complex named __ | “tenase”. |
| Tenase has two forms: | 1 Extrinsic: VIIa, III, and Ca2+
2 Intrinsic: IXa, VIIIa (cofactor),
phospholipid, and Ca2+ |
| is also known as “Fibrin stabilizing factor”.
It cross-links fibrin strands to form fibrin mesh.
This is where the platelet blood stabilizes and
complete coagulation. | Factor XIII |
| Factor Xa PROCESS | - It will then cleave the Prothrombin (II) to Thrombin (IIa) with the help of the cofactor, factor Va.
- The thrombin in turn cleaves Fibrinogen (I) into Fibrin (Ia).
- Thrombin also activates other factors in the intrinsic pathways such as factor XI and cofactors
VIII, V, and factor XIII.
- Factor XIII is also known as “Fibrin stabilizing factor”. It cross-links fibrin strands to form fibrin mesh.
This is where the platelet blood stabilizes and
complete coagulation. |
| Activated plates in Stages of
Hemostasis: | 1 Secrete serotonin leading to
Vascular spasm.
2 Become adhesive leading to
platelet plug
3 Site for Coagulation |
| They prevent blood loss during
wound healing but once the blood
vessels are repaired, they must be
dissolved to restore blood flow.
This process is called Fibrinolysis. | Blood clots |
| A small cascade that produces the
enzyme plasmin which cleaves
fibrin and dissolves the clot. | Fibrinolysis |
| Vitamin K is
important in the
activation of factors __ | 7, 9, 10, and 2 |
| These two may or
might lead to
excessive bleeding. | 1 Liver disease (cirrhosis,
hepatitis, cancer)
2 Vitamin-K deficiency |
| Drugs used to prevent thrombosis: | 1 Drugs that Inhibit platelet
aggregation:
a. Aspirin
b. Clopidogrel
c. Prasugrel
2 Drugs that inhibit coagulation:
a. Heparin
b. Warfarin |
