Facts About Blood in the Human Body
The type of blood a person has is determined by their genes. Each type of blood has a different combination of antibodies and antigens. The combinations are used to classify the blood into types. Even though there are different types of blood, all types are made up of the same basic parts. Blood is made up of cells that float in a fluid. That fluid is called plasma. The plasma is made of a combination of salts and proteins. Everyone has about four to six liters of blood in his or her body.
Types of Blood
The blood types are divided up into four blood groups and eight blood types, notes WebMD. The four basic groups are A, B, AB and O. The types are A-positive, AB-positive, B-positive ,O-positive, A-negative, AB-negative, B-negative and O-negative. The Rhesus (Rh) factor determines if a type is positive or negative. Blood that has this antigen is positive. If it does not have this antigen, it is negative. Before blood groups were discovered, many people died from blood transfusions because they were given the wrong type. Austrian scientist Karl Landsteiner discovered the blood types in 1901.
What Happens When Blood Types are Mixed
If a person is given the wrong type of blood during a transfusion, it can be deadly. However, if caught right away, it can be counteracted. When blood types mix, the blood can clot, states WebMD. Antibodies in the blood of the person receiving the transfusion will fight the cells of the new blood. This will cause a toxic reaction in the body. The blood from both parties needs to be in the same group. They do not have to be an exact match; they just need to be compatible. Usually, samples of the donor blood and recipient blood are mixed before a transfusion to make sure they combine well. This process is called crossmatching. Type O-negative blood is usually only used in an emergency, when a compatible type is in short supply or not available.
The American Red Cross encourages all blood types to donate blood. In the United States, someone needs a blood transfusion every three seconds. One pint of blood can be used in up to three people. That donated blood can be life-saving. Blood can be donated once every eight weeks, notes the American Red Cross.