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Plasma
1. The fluid component of the circulating blood
that is watery and straw-colored. Plasma is
separate from serum, which is the liquid part of
blood obtained after blood coagulates (turns
from liquid to solid form). This is the difference
between plasma and serum. White blood cells,
red blood cells, and platelets are suspended in
plasma. White blood cells help protect the body
against diseases and fight infections. Red
blood cells help carry oxygen to the blood.
Platelets are cells that help stop bleeding by
changing the blood from a liquid to solid form.
Diagram of blood plasma.
BOOK OF THE DAY: Hematology: Clinical Principles and Applications
Plasma is very important for carrying cell parts through the circulation, transporting
nutrients, maintaining the balance between acids and bases (opposites of acids) in the
body, and transporting wastes from the tissues. Plasma also plays an important role in
exchanging fluids and electrolytes between the tissues and capillaries (types of small
blood vessels). Electrolytes are chemical substances that are able to conduct electricity
after they are melted or dissolved in water.
Plasma helps maintain osmotic pressure with the interstitial fluid. Interstitial fluid is the
fluid outside of cells that fills the spaces between most cells of the body and forms a
significant part of the liquid of the body. Osmotic pressure is a type of pressure in liquid
that affects how substances move within it.
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Plasma is made of water, protein, fats, gases, glucose (a type of
blood sugar), electrolytes, and bilirubin. Bilirubin is a yellow-orange
substance found in bile. Bile is a bitter, yellow-green substance
released from the liver that carries away waste products. The liver
is the largest organ in the body and is responsible for filtering
(removing) harmful chemical substances, producing important
chemicals for the body, and other important functions. This definition
of plasma is sometimes referred to as blood. Other definitions of
plasma are described below.
2. The fluid component of lymph that is also watery and straw-
colored. Lymph is a milky fluid that contains proteins, fats, and white
blood cells (which help the body fight off diseases).
3. The fluid in which fat droplets of milk are suspended.
4. The so-called "4th state of matter" (besides liquid, gas, and solid) in which high temperatures cause
atoms to break down to form free electrons (negatively charged particles) and are essentially stripped
of their nuclei (the center of an atom). An atom is the smallest part of a substance that can exist and
still possess all of the properties that are characteristic of the substance. Plasma is produced in the
laboratory as part of hydrogen fusion (also known as thermonuclear) research. Hydrogen fusion is the
formation of more complex atomic nuclei (i.e., helium nuclei) from less complex nuclei (i.e., hydrogen
nuclei) with release of energy. Hydrogen is a type of non-metallic element that is the most common in
the universe. This definition of plasma is sometimes referred to as plasm.
5. Gas that is highly ionized (separated into ions). An ion is an atom or a group of atoms that have an
electric charge by gaining or losing one or more electrons. The word plasma is Greek for "something
formed."