A blood vessel may be damaged by transection (cutting across) or rupture.
At such points, a volume of whole blood can flow out of the blood vessels. This escape of
blood from the blood vessels is called hemorrhage.
HEMO = blood
RRHAGE = excessive flow ("bursting forth")
When this happens the bloods clotting system ………
Step 1 Vascular Contraction
Vascular contraction. The first response to a cut or ruptured vessels is contraction (spasm) of the blood vessel itself. This may considerably reduce the volume of blood loss.
Step 2 Platelet Plug
Platelet Plug. If the hole is small, a plug formed by clumping of the platelets
may be adequate to stop the bleeding.
Step 3 Blood Clotting
Blood Clotting. There is a complicated process for sealing off holes or ends of blood vessels after a cut or rupture.
By this process, called coagulation or clotting, the blood forms a solid mass to seal the opening where the blood is escaping. The mass is called a blood clot.
After many intermediate steps, the protein fibrinogen of the blood is converted into sticky strands of fibrin. These sticky strands adhere to the wall of the opening and form a meshwork in the opening, which traps RBCs and plasma. Thus, the opening is sealed.
Step 4 Hematoma
Hematoma. A hematoma is a collection of blood, usually clotted, in an organ, space, or tissue. When found immediately beneath the skin, it will produce a purplish spot or mark.
With time, as the clot is broken down and resorbed, the hematoma changes color and becomes smaller.
Step 5 Mobilization of Blood Reservoirs
Mobilization of Blood Reservoirs. Certain areas of the body contain enough blood that they can be used as reservoirs to maintain the circulating blood volume. This is important when a volume of blood has been lost through hemorrhage.
Among these are the spleen and the liver, whose sinuses together can release several hundred milliliters of blood. Also important are several groups of veins, including the large abdominal veins, which can also provide several hundred milliliters of blood.