Blood cells
Blood cells are made in the bone marrow (the inside of your bones). Once the cells are fully formed, they swarm out into the bloodstream where plasma transports them through the body. Once in the bloodstream, most blood cells have a limited lifespan. Red blood cells live for 120 days. White blood cells live for 2 days on average, and platelets only ten days. Enormous numbers of cells are broken down and replaced by new ones all the time in your body. There are three kinds of blood cells: red blood cells, white blood cells and platelets.
Red blood cells
Red blood cells (erythrocytes) are the largest proportion of blood cells. They transport oxygen through the body using hemoglobin, a protein that uses iron to bind oxygen to itself, making it the perfect transport medium for oxygen. A lack of hemoglobin and iron is called anemia.
White blood cells
White blood cells (leukocytes) are primarily designed to combat everything that does not belong to the body. When a person is given a blood transfusion, remaining white blood cells in the blood product may evoke an immune reaction when a patient has antibodies that recognize the white blood cells from the donor. These antibodies may be formed as a result of a previous transfusion or preganancy. The antibodies may start an immune reaction, with sometimes serious side effects. With the processing of blood in red blood cells, platelets and plasma, most of the white blood cells are removed. We futher filter the blood products to remove the last remnant of white blood cells. The filtering is done in all blood donations and is called general leukocyte depletion (GLD).
Platelets
Platelets (thrombocytes) allow blood to clot. If damage occurs to a blood vessel, the platelets stick to the blood vessel wall and to each other. They form a clot that closes the leak. Platelet deficiency can lead to spontaneous bleeding.
Plasma
Plasma consists of water in which proteins, minerals, fats and hormones are dissolved. It transports blood cells through the body and contains more than one hundred proteins, each of which has a different function. For example, the protein albumin has a water attracting function: it ensures water remains in the blood vessels and does not leak into the tissues. Plasma also contains clotting factors, proteins that work together with platelets in the clotting process.
Antibodies
Another important type of proteins in the plasma are the antibodies. These proteins protect the body against infectious diseases by binding to intruding viruses and bacteria. In this way they help the immune system to recognise intruders as foreign bodies, after which they are destroyed.