Plasma is the watery component of blood.  It accounts for a little over half of the blood volume.  Plasma is like vegetable soup with all the vegetables and noodles removed.  But don't be fooled, plasma plays a critical role in the body.  First of all, plasma is the "river" that delivers all the important stuff the body tissues need.  It is also removes waste products from the cell.  Red blood cells have no nucleus and are unable to move without the free-flowing plasma.

What are the functions of plasma?

Pressure - The fluid component of blood helps maintain blood pressure.  Fluid (unlike gases) are almost entirely non-compressible.  Fluids however can maintain pressure to keep the rubbery and flexible blood vessels wide open to allow blood cells to pass easily.

Flow - This may seem obvious, but plasma allows blood to flow.  Liquids (unlike solids) can easily flow from areas of high pressure to low pressure.  This is why blood flows from the heart and arteries (high pressure) to veins (low pressure).  This movement from areas of high pressure to areas of low pressure help explain by blood pressure changes with each heart beat.  When the heart contracts (during systole) high pressure develops.  When the heart and arteries relax (during diastole) the blood pressure decreases.

Delivery of heat - Plasma is one of the body's main ways to distribute heat.  This is similar to a heat pump in a house.  Heat is transferred from the hot areas and delivered to the cold areas.  If your body is too hot, heat will be removed from plasma that travels through blood vessels close to the skin.

Delivery of water - Blood plasma contains about 90% water.  This is the water source for all the body tissues.  Water is absorbed by the intestines and enters the blood directly or through lymphatic ducts.

Delivery of oxygen - Plasma is the fluid that delivers red blood cells to the lungs and then to the body tissues.  While most oxygen is held by the red blood cells, all oxygen must first travel through the plasma in order to reach the body tissues.

Delivery of nutrients - All foods that you eat are digested into tiny components that are transported through the blood plasma.  The only way for a cheeseburger to get from your stomach to your toes is throught the bloodstream.  Nutrients are delivered in the form of sugars (mostly glucose), amino acids, lipids and minerals.

Delivery of white blood cells - White bloods cells are the body's armed defenders against germs.  White blood cells must be deployed quickly and efficiently to sites of infection.  White blood cells flow through the blood until they reach the area of germ invasion.  Here, the white blood cells stick to the sides of blood vessels and wiggle through the tissues towards the germs.

Delivery of antibodies - Antibodies (also called immunoglobulins) are proteins that attach to germs.  These antibodies have a section that comes in millions of shapes (like a key).  Like a key in a lock, an antibody recognizes a very specific germ or germ part.  Once the antibody attaches, other white blood cells recognized the germ as "bad" and destroy it!

Delivery of clotting proteins - There are many different proteins that play a role in blood clotting and blood clot breakdown.  When a blood vessel is damages, the damages cells release chemicals that cause a chain of events called the "coagulation cascade."  Clotting proteins are activated in a way that leads to the formation of a fibrin net that holds blood cells and platelets in place. 

Delivery of transport proteins - Albumin is the body's most abundant transport protein.  Albumin is like an 18-wheeler truck that delivers important nutrients and other chemicals through the blood to all the parts of the body.  Albumin (and other proteins) also maintain the colloid pressure of the blood.  Colloid pressure is due to the attractiveness of water to plasma proteins.  The more protein in the plasma, the more water that is "held" inside the blood vessels.

Removal of waste products -  The major waste products from the body tissues are delivered to the kidneys by the plasma.  These waste products include urea and creatinine which are excreted in the urine.

Removal of carbon dioxide -  An important waste product of cellular metabolism is carbon dioxide.  Carbon dioxide dissolves in blood plasma (mostly in the form of bicarbonate ions).  In the lungs, carbon dioxide forms a gas and is exhaled.

What is fresh frozen plasma (FFP)?

Fresh frozen plasma (FFP) is a blood product that can be given in several different medical situations as a  transfusion.  Blood that is donated can be separated into multiple components including: red blood cells, platelets, and plasma.  This way, multiple patients can receive products from a single blood donation. 

Plasma is separated from the cellular components of blood and frozen.  When needed, this plasma is thawed and warmed.  It is then given to a waiting patient.  FFP is mostly used when a patient is sick or bleeding and has depleted the supply of clotting factors.

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