What is the difference between extrinsic and intrinsic blood clotting pathways?
The clotting cascade occurs through two separate pathways that interact, the intrinsic and the extrinsic pathway. The extrinsic pathway is activated by external trauma that causes blood to escape from the vascular system. This pathway is quicker than the intrinsic pathway. It involves factor VII.
What is the extrinsic pathway of blood clotting?
The extrinsic pathway consists of the transmembrane receptor tissue factor (TF) and plasma factor VII/VIIa (FVII/FVIIa), and the intrinsic pathway consists of plasma FXI, FIX, and FVIII. Under physiological conditions, TF is constitutively expressed by adventitial cells surrounding blood vessels and initiates clotting.
What is extrinsic and intrinsic system?
The extrinsic system operates as the result of activation by tissue lipoprotein, usually released as the result of some mechanical injury or trauma. The intrinsic system usually involves circulating plasma factors. Both of these pathways come together at the level of factor X, which is activated to form factor Xa.
What are the three 3 stages of Haemostasis blood clotting )?
1) Constriction of the blood vessel. 2) Formation of a temporary “platelet plug.” 3) Activation of the coagulation cascade. 4) Formation of “fibrin plug” or the final clot.
What is the major difference between the intrinsic and extrinsic coagulation cascades?
The main difference between intrinsic and extrinsic pathways in blood clotting is that intrinsic pathway is activated by a trauma inside the vascular system whereas extrinsic pathway is activated by external trauma.
What is the extrinsic pathway?
The extrinsic pathway of blood coagulation is also known as the tissue factor pathway and refers to a cascade of enzymatic reactions resulting in blood clotting and is done with the addition of injured tissue cells.
What happens in the extrinsic pathway?
The extrinsic pathway is the shorter pathway of secondary hemostasis. Once the damage to the vessel is done, the endothelial cells release tissue factor which goes on to activate factor VII to factor VIIa. Factor VIIa goes on to activate factor X into factor Xa.
What is intrinsic coagulation system?
All the components necessary for the clotting process to proceed are found in the blood. As such, the proteins required for such clotting to take place are part of the intrinsic pathway of blood coagulation.
What are the stages of homeostasis?
There are three stages of homeostasis. They are sensing, processing and responding. These stages are managed by the receptor, control center and effector respectively.
What are the processes of blood clotting?
Blood clotting normally occurs when there is damage to a blood vessel. Platelets immediately begin to adhere to the cut edges of the vessel and release chemicals to attract even more platelets. A platelet plug is formed, and the external bleeding stops.
How are the two pathways of haemostasis measured?
The two pathways and their measurement are explained below: Intrinsic pathway (measured by APTT) – Triggered by the exposure of collagen after a blood vessel is damaged. Extrinsic pathway (measured by PT) – Triggered by the release of thromboplastin from damaged endothelial cells.
Which is the intrinsic pathway of secondary hemostasis?
Intrinsic Pathway This pathway is the longer pathway of secondary hemostasis. It begins with the activation of Factor XII (a zymogen, inactivated serine protease) which becomes Factor XIIA (activated serine protease) after exposure to endothelial collagen.
What causes the release of intrinsic and extrinsic pathways?
Intrinsic pathway (measured by APTT) – Triggered by the exposure of collagen after a blood vessel is damaged. Extrinsic pathway (measured by PT) – Triggered by the release of thromboplastin from damaged endothelial cells. It can be released in response to breaking of the blood vessel wall, hypoxia, sepsis, malignancy and inflammation.
How is haemostasis related to the clotting cascade?
Haemostasis is the process of blood flow slowing in response to vessel injury. The process allows for blood clots to form via the clotting cascade in order to limit damage to the body and prevent excessive bleeding. Clotting factor function can be measured by the PT and APPT test, and platelet function can be measured by bleeding time.