outline the major features of the normal clotting process in the body, starting from the common pathwayonwards

Answer 1

The process of blood clotting and then the subsequent dissolution of the clot, following repair of the injured tissue, is termed hemostasis. Hemostasis, composed of 4 major events that occur in a set order following the loss of vascular integrity:

1. The initial phase of the process is vascular constriction. This limits the flow of blood to the area of injury.

2. Next, platelets become activated by thrombin and aggregate at the site of injury, forming a temporary, loose platelet plug. The protein fibrinogen is primarily responsible for stimulating platelet clumping. Platelets clump by binding to collagen that becomes exposed following rupture of the endothelial lining of vessels. Upon activation, platelets release adenosine-5'-diphosphate, ADP and TXA2 (which activate additional platelets), serotonin, phospholipids, lipoproteins, and other proteins important for the coagulation cascade. In addition to induced secretion, activated platelets change their shape to accommodate the formation of the plug.

3. To insure stability of the initially loose platelet plug, a fibrin mesh (also called the clot) forms and entraps the plug. If the plug contains only platelets it is termed a white thrombus; if red blood cells are present it is called a red thrombus.

4. Finally, the clot must be dissolved in order for normal blood flow to resume following tissue repair. The dissolution of the clot occurs through the action of plasmin.

Two pathways lead to the formation of a fibrin clot: the intrinsic and extrinsic pathway. Although they are initiated by distinct mechanisms, the two converge on a common pathway that leads to clot formation. The formation of a red thrombus or a clot in response to an abnormal vessel wall in the absence of tissue injury is the result of the intrinsic pathway. Fibrin clot formation in response to tissue injury is the result of the extrinsic pathway. Both pathways are complex and involve numerous different proteins termed clotting factors.

Answer 2

Well, this pretty much outlines the process in the form of equations.

1. Injured tissues + blood platelets --> release thromboplastin

2. Prothrombin ----> Thrombin (in the presence of thromboplastin and Ca ions)

3. Fibrinogen ----> Fibrin ( in the presence of thrombin formed in 2.)

4. Fibrin + Red blood corpuscles ---> blood clot

Answer 3

an injury which ruptures a blod vessel may cause immense blood loss, which may even lead to death. body has its own mechanism of preventing this loss by forming a blood clot which plugs the injury to stop bleeding. clotting or coagulation is a complex process involving many steps and factors.
1) when tissues get damaged, along with platelets an enzyme called thromboplastin is produced.
2) it acts on plasmaprotein in presence of calcium ions and forms prothrombokinase enzyme.
3) it acts on another plasmaprotein, inactive prothrombin, inactive prothrombin which is formed in liver, and converts it into active thrombin.
4) it acts on inactive fibrinogen, a plasmaprotein and converts it into active fibrin.
5)fibrin is the ultimate product which forms a mesh into which red blood corpuscles get entangled to form a blood clot.

clotting does not happen in the blood in the body because of heparin. it does not allow prothrombin to change to thrombin. heparin becomes inactive during injuries due to action of air. vitamin K is also important for blood clotting as it helps in synthesis of prothrombin