Adhesions form as a natural part of the body’s healing process after surgery in a similar way that a scar forms. The term "adhesion" is applied when the scar extends from within one tissue across to another, usually across a virtual space such as the peritoneal cavity. Adhesion formation post-surgery typically occurs when two injured surfaces are close to one another. According to the "classical paradigm" of adhesin formation, the pathogenesis starts with inflammation and activation of the coagulation system which causes fibrin deposits onto the damaged tissues. The fibrin then connects the two adjacent structures where damage of the tissues occurred. The fibrin acts like a glue to seal the injury and builds the fledgling adhesion, said at this point to be "fibrinous." In body cavities such as the peritoneal, pericardial, and synovial cavities, a family of fibrinolytic enzymes may act to limit the extent of the initial fibrinous adhesion, and may even dissolve it. In many cases, the production or activity of these enzymes are compromised because of inflammation following injury or infection, however, and the fibrinous adhesion persists. A more recent study suggested that the formation of "fibrinous" adhesions is preceded by the aggregation of cavity macrophages, that can act like extravascular platelets in the abdominal cavity.