When Does Blood Congeal?
Blood congeals when a part of the body is wounded. If it failed to congeal the injured person would die from loss of blood. The congealing, or coagulation, of the blood, is the first step towards healing a wound. It closes the wound and builds a scaffold for new tissue by means of a chemical process in the plasma, the fluid part of the blood.
In this process the platelets (small cellular bodies in the blood) produce thromboplastin. This changes fibronigin, a protein in the blood, into fibrin. Finally a spongy network of fibrin connects the edges of the wound and prevents the loss of any more blood cells. Often, a scab is formed over the wound as a protection.
Many factors, such as diseases, disorders, and medications, can impact the amount of time it takes for blood to clot. There are 13 different clotting factors involved in blood coagulation, according to the National Hemophilia Foundation. If there is a deficiency in production, or if the body produces a defective form, then an individual may develop a bleeding disorder. Depending on how extreme the condition is, the disorder can cause mild symptoms such as nosebleeds to severe symptoms such as internal bleeding. Medications, such as aspirin, heparin and warfarin, in the bloodstream also impact coagulation.
In the case of a cut or rupture of the blood vessel wall, the escaping blood comes into contact with collagen (contained in the tissues which surround the blood vessel). This contact triggers off the coagulation process. Initially this is a series of complex chemical reactions, lasting about three minutes, and involving trace protein and tissue factors. Then the soluable Fibrinogen gets converted into the insoluble protein Fibrin., and in 10 to 12 minutes, this Fibrin has formed an initial barrier over the wound, initially a soft clot containing serum and blood cells.
Under the action of coagulation factor XII, this clot shrinks, expelling the liquid serum that it contains. In 1 to 3 hours, the quantity of serum ejected corresponds to about half the volume of the initial clot. If the coagulation takes place on the exterior surface of the body, the clot dries to form a scab (we have all seen this on our own skin after a scratch or cut).
If the coagulation takes place inside the body, the clot stays humid, and does not dry to a scab. Most of us will have noticed, on the dressings and bandages that have protected wounds, that there is often a sort of clear halo around the central point ; this halo is formed by exuded serum, containing mineral salts, proteins and water.
The blood cells in the clot contain most of the elements that were present in the cells in the blood, notably haemoglobin, the main constituant of red cells, and some antigens, such as those responsible for the different blood groups A, B, AB, rhesus, that we normally find in the red blood cells.