Coagulation

Coagulation Blood Clotting Very complex process Balance between clotting factors—some promote coagulation and some inhibit it Normally anticoagulants prevail but in trauma or injury, coagulation factors increase and clotting occurs

Process of coagulation when tissue damage occurs Prothrombin activator produced (depended on calcium) Prothrombin converted to thrombin Thrombin acts as an enzyme—causes reaction in fibrinogen Fibrinogen molecules join forming fibrin

Fibrin sticks to the edge of damaged blood vessels and form meshwork for platelets and blood cells—blood clot forms

Once the clot appears—promotes more clotting—positive feedback mechanism—thrombin causes more prothrombin—causes more thrombin Unstable condition Movement of blood normally prevents massive clot formations

Clotting ceases when clot comes in contact with moving blood Plasma protein is released which digests fibrin threads—most clots dissolve in time Embolus—dislodged or fragment of clot abnormally in vessel—moves until it becomes lodged in small vessel—interferes with blood flow to the area

http://www.blobs.org/science/cells/clottingcascade.gif

Blood groups Antigens Proteins on rbc membrane surface A, B, Rh

Antibody a. Proteins in plasma b. Anti A, Anti B are formed naturally Rh group a. Anti Rh does not appear spontaneously—only after exposure

http://faculty.weber.edu/nokazaki/Human_Biology/Chp%207-blood_files/image016.gif

ABO Blood Groups Type Antigen Antibody A Anti B B Anti A O None Anti A, Anti B AB A and B none