An erythrocyte is the medical term for a red blood cell. "Erythro" refers to the color red, and "cyte" refers to a cell. Red blood cells are responsible for the transportation of oxygen to every cell of the body except those of the epidermis, the outer layer of the skin, which does not contain any blood vessels. Erythrocytes also are responsible for carrying carbon dioxide away from the body's cells. If an erythrocyte is viewed under high magnification, it appears red and round in shape, somewhat like a small doughnut, but it is sunken in the middle rather than having a hole.
Without oxygen, the cells that make up the tissues and organs of the body, including the brain, cannot survive. Likewise, the cells also must constantly be rid of carbon dioxide. Although the erythrocyte is a cell itself, it is unique in that it is not only oxygenated but also has the ability to supply oxygen to other cells to keep them alive. Carbon dioxide is a waste product that must be removed from the body, and the red blood cell functions to rapidly transport this harmful substance away from cells. The erythrocyte, however, like other cells, has a life span, which is why the there is a filtration system in the spleen that removes old blood cells from circulation.
Many people who are not health care providers might assume that erythrocytes are blood or a medical term that can be used to refer to the blood; however, such use of the word is not completely accurate. Red blood cells are just one of four components that make up the liquid that is called blood. Leukocytes, plasma and platelets are the other components of blood. Leukocytes are white blood cells responsible for the destruction of microorganisms and the production of antibodies that help the body to protect itself against infection.
Plasma is a watery fluid that actually makes up more than half of the liquid that most people call blood. This salty fluid is of extreme importance because it is the substance in which the body's erythrocytes, leukocytes and platelets are carried. Platelets are special cells enclosed by a membrane; when activated, they release chemical factors involved in the formation of blood clots. Clotting is essential to help prevent a person with an open wound from losing dangerously high amounts of blood, which would result in a condition known as shock or could even result in death.