Blood plasma got its name from the Greek word “plasma,” meaning “something molded or created.” The Czech scientist Jan Evangelista Purkyně introduced the term in the 1800s to describe the fluid portion of blood, likely because this straw-colored liquid serves as a moldable medium that carries blood cells and gives blood its flowing form.
The Greek Root Behind the Name
The word “plasma” traces back to the Greek verb “plassein,” meaning to mold or shape, and originally “to spread thin.” By the early 1700s, English borrowed the Late Latin form “plasma” to mean “form” or “shape” in a general sense. The word shares its deep roots with the Proto-Indo-European root *pele-, which meant “flat” or “to spread.”
When Purkyně needed a name for the clear, yellowish fluid that remained after blood cells were removed, “plasma” fit. The fluid is, in a real sense, the moldable substance that holds everything else in blood together. It flows, it spreads, it takes the shape of whatever vessel contains it, and it carries a complex mixture of cells, proteins, and nutrients suspended within it.
What Purkyně Saw in the Microscope
Jan Evangelista Purkyně (1787–1869) was a pioneering Czech physiologist who spent much of his career studying cells and tissues under the microscope. He introduced two related terms that stuck: “protoplasm” for the living material inside cells, and “plasma” for the fluid portion of blood. Both words lean on that same Greek idea of something moldable and formative. In Purkyně’s view, blood plasma wasn’t just passive filler. It was the medium that shaped and sustained everything flowing through the circulatory system.
What Blood Plasma Actually Is
Plasma makes up about 55% of your total blood volume. It is 91% to 92% water, with the remaining 8% to 9% consisting of dissolved solids. Those solids include proteins like albumin (which helps maintain fluid balance), immune proteins called immunoglobulins (which fight infections), clotting proteins like fibrinogen (which stop bleeding), and electrolytes like sodium, potassium, and calcium that help regulate blood pH.
If you let blood clot and then separate the liquid from the clot, you get serum, not plasma. The difference is that plasma still contains fibrinogen and other clotting factors, while serum has had those removed during the clotting process. This distinction matters in medicine: plasma transfusions are used specifically because they deliver those clotting factors to patients who need them, such as people with severe bleeding, liver disease, or clotting disorders.
Why Physics Borrowed the Same Word
If you’ve heard “plasma” used to describe the superheated ionized gas in stars, lightning, or plasma TVs, that’s a separate borrowing of the same Greek word. The physicist Irving Langmuir proposed the term in 1928 to describe a region of balanced ions and electrons. No one recorded exactly why he chose it, but there are two leading theories. One suggests that because ionized gas in neon lighting can be molded into almost limitless colorful shapes, “plasma” captured that flexibility. The other, favored by Langmuir’s colleague Lewi Tonks, is that Langmuir was directly inspired by blood plasma: just as blood plasma carries different types of cells (red cells, white cells, platelets), ionized gas carries different species of particles (electrons, ions, neutral atoms).
Either way, the connection loops back to that original Greek meaning. Whether it’s the fluid in your veins or the glowing gas inside a star, “plasma” describes a shapeable medium that carries distinct components within it.