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Erythrocyte

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Definition

noun, plural: erythrocytes

A blood cell with hemoglobin-rich cytoplasm and whose main function is to transport respiratory gases, chiefly oxygen


Supplement

Blood is the circulating fluid in the body of eukaryotic animals. It is primarily composed of plasma and cellular elements (blood cells and platelets). A majority of the cellular elements is the red blood cells. A mature red blood cell is termed an erythrocyte.

An erythrocyte is the blood cell involved in the transport of respiratory gases, particularly oxygen and carbon dioxide. Oxygen molecules move into the erythrocytes from the air inspired via the respiratory organs (e.g. the lungs of terrestrial vertebrates or the gills of fish). The erythrocytes deliver the oxygen (via the circulatory system) to hypoxic tissues needing oxygenation. With the release of oxygen molecules, most carbon dioxide molecules (from tissues diffusing into the blood plasma) move into the erythrocytes to be transported and eventually released outside via the respiratory system. In humans, carbon dioxide molecules from the erythrocytes are released as bicarbonate ions into the plasma and then converted back to carbon dioxide upon reaching the alveolar space in lungs to be expired.

The presence of high concentration of hemoglobin in the cytoplasm of erythrocytes enables the transport of respiratory gases, mainly oxygen. The hemoglobin binds with oxygen molecules. Each hemoglobin has an affinity for four oxygen molecules. When oxygenated, it renders the erythrocyte red, thus, accounting for the color of the cell. The hemoglobin may also pick up few carbon dioxide but most of the carbon dioxide diffusing into the erythrocyte react with water molecules, forming carbonic acid (which later dissociates into bicarbonate ion and hydrogen ion). Most of the hydrogen ions attach to hemoglobin and other proteins to control the acidity of blood and thereby maintain the normal pH of blood.

Most vertebrates have red blood cells that remain nucleated. However, in mammals including humans, the mature red blood cells are biconcave and anucleated. The crocodile icefish of family Channichthyidae is the only vertebrate group to naturally lack erythrocytes and obtain oxygen from their oxygen-rich aquatic habitat via passive transport.



Word origin: Latin erythro- (“red”) +‎ -cyte (“cell”)

Also called:

  • red blood cell
  • red blood corpuscle
  • haematid
  • erythroid cell

See also:

Related term(s):

Related form(s):

  • erythrocytic (adjective, of, pertaining to, or relating to an erythrocyte)