Plasma is a clear yellowish liquid that forms the fluid portion of blood and lymph. Plasma transports red and white blood cells and platelets throughout the body. It also delivers nutrients to the body's millions of cells and picks up cell waste products.

Plasma is composed chiefly of water. This watery solution contains small amounts of minerals, salt, sugar (glucose), fats, amino acids, hormones, enzymes, dissolved gases, wastes like urea, and several proteins. One such protein is fibrinogen, the substance chiefly responsible for blood clotting. Other important proteins transport vital chemical elements such as iron and copper through the bloodstream, which help maintain the fluid balance of the body. Plasma proteins known as gamma globulins are antibodies that help protect the body against invasion by bacteria or viruses.