Blood and Blood Disorders Health Article

Blood characteristics

Specific proteins, known as antigens, on the surface of the red blood cells and in the plasma differentiate the types of blood. There are two main categories of the special proteins, known as Type A and Type B. Thus, individuals fall into one of four main blood type groups based on combinations of these special proteins. The table illustrates the special protein composition of each blood type. Another feature of blood is the Rh factor. The Rh special protein is either present or absent in blood, leading to the labels of Rh positive (protein present) and Rh negative (protein absent). When a pregnant woman and her fetus are of different Rh types, problems in fetal development may occur. The Rh factor is also matched when selecting blood for transfusions.

Blood is collected and stored according to type and Rh factor for use in transfusions. The blood categorized as Type O (neither Type A nor B proteins present) and Rh negative is generally considered to be a universal donor, that is, blood of this type may be accepted by anyone, no matter what their blood type. Because of increased concern over the possibility of contracting a disease through a blood transfusion, individuals may elect to donate their own blood weeks before an elective surgical procedure to ensure compatibility and freedom from new diseases. In many hospital settings, donors may give blood designated for use by a specific patient.

Blood disorders

There are a number of disorders that affect the health and functioning of the blood. Causes of blood disorders range from genetic abnormalities (as in sickle-cell anemia) to environmental factors (as in hemorrhage associated with vitamin-C deficiency). Among the most common blood disorders are anemia, a condition in which there are too few red blood cells; polycythemia, the counterpart to anemia, where there are too many red blood cells; leukemia, a type of cancer in which the blood has too many white blood cells; and thrombosis, a condition where the blood clots too readily. Blood poisoning is a layperson's term for any infection (from mild to life-threatening) affecting the blood or its components. For example, when bacteria invade the blood (often through an injury) and multiply, the condition is known as septicemia. When excessive amounts of toxins are produced, the condition is called toxemia.