Hemostasis is the process of how the body stops bleeding from a cut or injury. This involves forming a clot to close the hole in the blood vessel and repairing the blood vessel.
When a blood vessel is injured, platelets stick together to form a plug. Proteins, called clotting factors, interact to form a fibrin mesh to hold the platelets in place. This allows the injury to heal while preventing blood from escaping the blood vessel.
Generally, control of bleeding is achieved very quickly through the formation of a clot. In major trauma or surgery, physicians often need to help patients to achieve adequate hemostasis - in order to minimize blood loss and related injury.
However, some people are born with a bleeding disorder (congenital) that impairs their ability to achieve hemostasis. An example of this is the hereditary disorder hemophilia.
As well, some people who have never had any bleeding problems can develop a condition that causes them to bleed, known as "acquired hemophilia".