The Role of Blood Clotting Mechanisms in Body
Blood is an extremely necessary component of the human body, as it helps in the entry of oxygen to tissues and cells. The organism protects the human body against blood loss through the coagulation mechanism, where the action of vascular mechanisms, such as platelets, coagulation factors, prostaglandins, enzymes, and proteins, are important for contributing to the formation of clots and the stagnation of blood clots.
Blood in an injured tissue
Coagulation is a biological process that prevents the extravasation of blood. When our skin is injured, bleeding will cause a “domino effect”, a kind of biological effect, in which a series of steps are triggered. The process is known as coagulation cascade, which results in the formation of a blood clot.
When the clotting cascade works correctly, blood is held at the site of injury, and bleeding is stopped; however, when there are people who have a bleeding disorder, however, they are unable to produce clots that block the process of blood leakage.
In a simplified way, the clot is formed after injury to the skin, resulting in bleeding due to the presence of blood vessels; then, to control blood loss, the blood vessel narrows, giving rise to a process we call vessel constriction, limiting the flow of blood in the blood vessel.
After this process, in response to injury, platelets are activated, contributing to the formation of a kind of “plug”. During the formation of the “plug”, a protein, called von Willebrand, contributes together with the platelets to stick to each other and to the wall of the blood vessel. Then, the clotting factor proteins trigger the production of fibrin, a substance that helps the plug to be firm and stable. Eventually, over the next few days to weeks, the clot strengthens and dissolves as the blood vessels regenerate, i.e., heal.
Coagulation tests
For the evaluation of coagulation, the doctor requests the coagulogram, which corresponds to a group of blood tests requested, to evaluate the coagulation process, thus identifying the treatment for the person in order to avoid complications. The coagulogram is also requested before surgeries so that the risk of the patient suffering bleeding during the surgical procedure is evaluated.
Several pieces of equipment, such as the ECL 760, are used to measure exams that are part of the coagulogram, such as PT and APTT, exams considered as coagulation screening tests. Image 1. ECL 760, a hemostasis device from Erba Mannheim
The TTP or APTT (Activated Partial Thromboplastin Time) test is used to detect deficiencies or inhibitors of intrinsic and common pathway clotting factors. That is, it evaluates factors XII, XI, IX, VII, X, V, II, and fibrinogen. In addition, it is also used for monitoring heparin-based anticoagulants. As seen, TAP and TTPA tests are used to assess possible disorders in blood clotting, which may result in a disease, which encompasses clotting factors and fibrinogen, hemorrhages, and even the therapeutic monitoring of anticoagulants.
By: Juliana Oliveira, Scientific Advisor and Master in Pathology-UFF
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