Plasma is the liquid portion of the blood. This slightly yellow fluid is made up of 90 percent water, according to the Franklin Institute. Although often thought of as less important than the cells of the blood that carry oxygen and provide immunity, the plasma is equally important. It is responsible for many different functions in the body.

Transport Nutrients

One of the most important functions of the plasma is to transport nutrients throughout the body. As food is digested in the stomach and intestines, it is broken down into its components. This includes amino acids (the building blocks of proteins), lipids (fats), sugars (glucose) and fatty acids. These nutrients are distributed to cells throughout the body where they are utilized to maintain healthy functions and growth.

Transport Waste

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In addition to transporting nutrients, the plasma transports waste products, such as:

• uric acid
  
• creatinine
  
• ammonium salts
  
• from the cells of the body to the kidneys

The kidneys filter these wastes out of the plasma and excrete them from the body as urine.

Maintain Blood Volume

Approximately 7 percent of the plasma is protein, according to the Science Encyclopedia 1. The protein found in the highest concentration in plasma is albumin, a protein important for tissue repair and growth. This high concentration of albumin is important for maintaining the osmotic pressure of the blood.

Albumin is also present in the fluids that surround the cells, known as the interstitial fluid. The concentration of albumin in this fluid is lower than in plasma. Because of this, water is not able to move from the interstitial fluid into the blood. If the plasma did not contain so much albumin, water would move into the blood, increasing blood volume and causing an increase in blood pressure which would make the heart work harder.

Balance Electrolytes

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Plasma carries salts, also called electrolytes, throughout the body. Without these salts, muscles would not contract and nerves would not be able to send signals to and from the brain.

Defend the Body

Plasma carries other proteins besides albumin throughout the body. Immunoglobulins, also known as antibodies, are proteins that fight off foreign substances, such as bacteria, that invade the body. Fibrinogen is a protein necessary to help the platelets (cells in the blood) to form blood clots. By carrying these proteins, the plasma is playing a critical role in defending the body against infection and blood loss.