In general, human blood — and most animal blood too, for that matter — is made up of two main components. Cellular matter holds the bulk of blood’s importance, at least on a physiological level; it includes red blood cells, white blood cells, and platelets. Each of these has a unique and important role in overall health and body functioning. Fluid materials help the cellular matter move from place to place, and provide the viscosity needed to keep everything held together. Plasma is one of the most important components in this category, which itself is made mostly of salt and water. In healthy people, both cellular and fluid materials are held together in suspension. Separating out the elements, as is sometimes required for certain diagnostic testing or medical transfusion purposes, generally requires specialized equipment.
Understanding Blood Composition Generally
Despite its relatively simple appearance, blood is considered by most health experts to be a remarkably complex substance. It is responsible for maintaining the health and functioning of most internal organs, fighting infection and providing immune support, and delivering oxygen to the heart and brain, among other things. Understanding the role of each of the key components can help people realize and appreciate the many roles of this substance.
Red Blood Cells
The cellular portion of blood contains several different types of cells and cell fragments. Red blood cells, which are known scientifically as erythrocytes, are the most numerous of these. The red blood cells use a molecule called hemoglobin to transport oxygen from the lungs to tissues in the body and to help move carbon dioxide back to the lungs to be removed. This makes them absolutely essential to growth and functioning. Mature red blood cells lack nuclei and organelles, and have a distinct biconcave shape that greatly increases surface area.
White Blood Cells
White blood cells are less numerous, but no less important. These are also called leukocytes and their main job is to help the immune system fight infection. They are created in the bone marrow and course throughout both the blood and the lymphatic tissue system.
Platelets, commonly known as thrombocytes in the medical community, are another key part of the blood’s cellular makeup. These are fragments of large cells called megakaryocytes and are a key element in forming blood clots. They help the blood clump together to prevent massive loss, and can also work to plug holes in broken vessels and arteries.
Plasma is another important blood component, but it is a fluid rather than a single cell. It is made of a matrix of water and numerous dissolved materials, including glucose, proteins, minerals, and carbon dioxide. Plasma is the fluid that carries blood cells through the body; without it they’d have a much harder time getting from place to place, and would not be as effective. Blood serum is the portion of plasma that has nutrients and other dissolved materials but lacks clotting proteins.
It can be hard to recognize these individual components on sight alone. Blood usually just looks like a thick, viscous red liquid. Seeing the different pieces in isolation almost always requires specialized equipment.
Blood processing is the technique of differentiating blood components from each other. For example, a hematocrit is a tube that is lined with an anti-coagulant, such as heparin, that contains blood and is placed in a centrifuge. This causes the cells pull away from both each other and their liquid suspension. Various blood processing techniques can be used during blood component therapy. For example, if a patient specifically needs platelets, these can be extracted from the whole blood and given in a blood transfusion.
Considerations for Transfusions and Donations
There are often instances, usually during a medical emergency, in which a person needs a blood transfusion. A transfusion is a process through which blood from someone else is injected into the patient, usually through an intravenous needle. Both blood and plasma can be transfused this way, and many hospitals and clinics have donation centers where healthy people can donate their blood. Sometimes donations are made with one specific patient in mind, but more often they’re done generally and are deposited in a “blood bank” where they can be used wherever needed most.
During blood component therapy that involves transfusion of the cellular portion of blood, it typically is important to find blood of the same type. All cells in the body have specific markers on their cell membranes called “antigens.” If blood cells with antigens that do not match the host are injected during a blood transfusion, serious consequences can follow, including death in some cases.