The idea of hemostasis is used to refer to the interruption of a hemorrhage , either by a chemical means, a physical means or spontaneously. A hemorrhage, meanwhile, is the blood flow that is generated when a blood vessel breaks.
Hemostasis, therefore, is a mechanism that causes stopping a bleeding process . Thanks to hemostasis, blood stops flowing and stays in the blood vessels.
Typically, the blood can circulate freely through the vessels. If a vessel ruptures, bleeding occurs (blood leaves the vessel). What hemostasis does is, at first, form a clot so that the bleeding stops. Then the organism is responsible for the repair of the damage and, finally, dissolves the clot. In this way the blood circulates normally again through the blood vessels.
If we analyze this process in detail, we will find that hemostasis consists of several phases . It starts with the reflex vasoconstriction , an immediate transient response to damage to a blood vessel that generates the sympathetic nervous system (One of the parts of the autonomic nervous system; is responsible for the regulation of various actions, such as the contraction of certain muscles and the secretion of several glands).
Reflex vasoconstriction results in a vascular spasm that reduces the diameter of the vessel and thus causes the bleeding to be delayed. On the other hand, it promotes the movement of cells of blood, bringing them closer to the site of the lesion to facilitate the interaction between the subendothelium and platelets.
The second phase of hemostasis is called primary hemostasis . It is the process by which the "platelet plug" is formed, and begins a few seconds later than vascular trauma. Its formation takes place because of the force with which platelets stick to the free collagen of the damaged vessel and the release of various chemical substances that increase platelet aggregation, which favors Union between the different elements
Thirdly we have the secondary hemostasis , which in everyday speech is known by the name of coagulation. It happens because the change The chemical that passes through the fibrinogen makes it insoluble and allows it to entwine with other molecules of the same type to give rise to large macromolecular aggregates that join in a three-dimensional network. Once it is transformed, the fibrinogen is renamed fibrin.
This coagulation process is complex enzymatic and carries the transformation of the fibrogen and its subsequent polymerization and crosslinking. It is important to note that clot formation does not always occur correctly, but sometimes certain alterations occur that cause late bleeding, such as bruising.
The last phase of the hemostasis process is called fibrinolysis and consists of the disintegration of the clot formed in the previous one. Once the healing process begins, the cells responsible for the formation of the tissue again they reach the clot and gradually degrade it. The name of this phase refers to the aforementioned fibrin, which is precisely the component that keeps the clot attached to the vascular wall. The enzyme that catalyzes fibrinolysis is called plasmin, a serine that is produced from an inactive precursor called plasminogen and can be activated by different factors, such as coagulation.
It should be noted that hemostasis can be induced with drugs or through the manual compression of the wound , for example. Thus people are able to act against bleeding beyond the spontaneous action of the organism.