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Have you ever thought about how our body prevents us from bleeding to death when we get injured? The coagulation cascade is the mechanism in charge of this and just as any other, it is very well regulated in order to respond as soon as a leak is detected.

The coagulation process is divided into two phases, the primary and the secondary hemostasis. This division is based on the main actors of each phase but both of them happen simultaneously. Let´s see how this works.

Primary hemostasis:The cellular phase 

The main purpose of this phase is to stop the bleeding as soon as possible and avoid more blood loss. It starts with the detection of a rupture in a blood vessel, which can be present in any tissue or any organ.

When a blood vessel is damaged, the inside of its lining gets exposed and gets into direct contact with the blood.

The exposure of a specific protein, known as collagen, and the Von Willebrand coagulation factor start the coagulation process by attaching to the platelets that are traveling at that exact time-point through the bloodstream. Platelets start then to aggregate at the site of the injury and they also start releasing substances that function as messengers, which attract more platelets to the area.

Secondary phase: The coagulation factors phase

At the same time, the coagulation factors start doing their job.

There are 13 coagulation factors that participate in a cascade of messages that promote the stabilization of the already formed platelet aggregate. It is called cascade because factors activate one after the other, in a specific order.

The messages initiate with the activation of the tissue factor and factor VIIa, which activate factor X and convert it into Xa (or X activated). Factor Xa activates prothrombin and converts it into thrombin, which main role is to transform fibrinogen into fibrin. As already said, this last one is the protein that forms a sort of net and attaches platelets between themselves and onto the wall of the blood vessel. Factor XIII stabilizes the fibrin net by doing some final stitches to it. 

Coagulation disorders 

There are many actors in this play and so an alteration to any of them can cause a disruption in the whole process. This is how problems with coagulation arise, giving origin to several diseases.

For example, a low number of platelets or thrombocytopenia, can lead to the formation of bruises and nose bleedings, and can be caused by nutritional deficiencies or even by cancer.

Thrombocytosis on the other hand, refers to an increase in the platelet count and can also be a result of a cancerous process, as well as part of an inflammatory response or as a result of the consumption of certain medications.

Hemophilia is probably one of the most known coagulation related disease.

This is a hereditary health problem, which mainly affects men, and it is caused by a deficiency of either coagulation factor VIII or IX.

Patients with this disease suffer from massive external and internal bleedings and are treated with synthetic factors that promote coagulation when it is needed. Because of this, they need to be very careful and avoid exposure to injuries as much as possible. Probably one of the most famous cases of hemophilia was that of Alexei Romanov, the son of Nicholas II and the last emperor of Russia.

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