Blood is composed of red blood cells, white blood cells, platelets, and a liquid component called plasma. Making up approximately 55% of blood’s volume, plasma serves as the transport medium for these cells. The extraction of plasma from whole blood is a standard procedure in modern medicine, enabling numerous therapeutic and diagnostic applications.
The Composition of Blood Plasma
Plasma is a straw-colored liquid that is about 92% water. The remaining portion contains a complex mixture of dissolved substances, with proteins being the most abundant. The most prevalent plasma protein is albumin, which is responsible for maintaining oncotic pressure, preventing fluid from leaking out of blood vessels. Albumin also acts as a carrier, transporting hormones, vitamins, and other substances.
Another significant group of proteins is the globulins, which are divided into alpha, beta, and gamma types. Alpha and beta globulins transport lipids and fat-soluble vitamins, while gamma globulins, also known as immunoglobulins, are integral to the immune system’s response to infection. Fibrinogen is another protein found in plasma, and its conversion to fibrin threads is a step in the formation of blood clots. Beyond these major proteins, plasma also carries electrolytes, hormones, glucose, and waste products.
Methods of Plasma Separation
The primary method for separating plasma from whole blood in a laboratory is centrifugation. This process involves spinning an anticoagulated blood sample at high speeds, which causes the denser components to settle at the bottom of the tube. The red blood cells, being the heaviest, form a layer at the bottom, followed by a thin layer of white blood cells and platelets, with the lighter plasma remaining on top. Once separated, the plasma can be carefully removed with a pipette.
A different method, apheresis, is employed for collecting plasma from donors. During apheresis, a donor’s blood is drawn through a specialized machine that separates the plasma from the other blood components. The machine retains the collected plasma while returning the red blood cells, white blood cells, and platelets to the donor’s circulatory system. This process allows for the collection of a larger volume of plasma compared to a standard whole blood donation.
Applications of Extracted Plasma
Extracted plasma has numerous applications in medicine, ranging from direct patient treatment to the production of specialized medical products. In hospital settings, plasma is transfused to patients who have experienced significant blood loss from trauma or surgery. It is also used to treat individuals with severe liver disease or those who have deficiencies in certain clotting factors, helping to manage or prevent bleeding episodes.
A large portion of donated plasma undergoes a process called fractionation, where it is pooled with plasma from thousands of other donations. This process separates and purifies specific proteins, resulting in a range of concentrated medical treatments. These include immunoglobulin therapies for individuals with immune system disorders, albumin solutions for burn victims, and specific clotting factor concentrates for conditions like hemophilia.
Plasma also serves as a resource in scientific research and diagnostics. Researchers use plasma to study the mechanisms of various diseases and to develop new treatments. In a diagnostic context, plasma is analyzed in laboratory tests to measure levels of hormones, electrolytes, and other biomarkers that provide information about a person’s health status.