A red blood cell, or corpuscle; one of the formed elements in the peripheral blood. For immature forms see normoblast, metarubricyte. In most mammals mature erythrocytes are biconcave disks that have no nuclei. The degree of concavity varies between species, as does the size. Birds have nucleated, oval erythrocytes. The cell consists mainly of hemoglobin and a supporting framework, called the stroma. Erythrocyte formation (erythropoiesis) takes place in the red bone marrow in the adult, and in the liver, spleen and bone marrow of the fetus. Erythrocyte formation requires an ample supply of certain dietary elements such as iron, cobalt and copper, amino acids and certain vitamins.
- e. antigen — see blood group antigen and blood group.
- e. casts — see urinary cast.
- e. count — see blood count.
- e. ghosts — in new methylene blue, erythrocytes fail to take up stain and appear only as a pale outline.
- hypochromatic e. — see hypochromia (2).
- e. indices — calculated values for the mean corpuscular volume (mcv), mean corpuscular hemoglobin (mch), and mean corpuscular hemoglobin concentration (mchc), taken from the hematocrit, hemoglobin concentration and red blood cell count. Used in determining the likely etiology of anemias and other abnormalities of the erythron. Called also mean cell constants.
- matchstick e. — describes the appearance of sickled deer erythrocytes containing hemoglobin II.
- normochromic e. — see normochromia.
- e. refractile bodies (ERF) — a term usually used to describe Heinz bodies in the erythrocytes of cats. Sometimes restricted in definition to the smaller (Heinz) bodies that are normally found in up to 10% of feline erythrocytes, as distinct from larger bodies associated with hemolytic anemia.
- e. sedimentation rate (ESR) — an expression of the extent of settling of erythrocytes in a column of fresh citrated or otherwise treated blood, per unit of time. Of greatest diagnostic value in dogs as horses normally have a greatly accelerated rate and ruminants show none except in very extreme circumstances. In the dog, ESR is elevated with inflammatory processes. See also sedimentation rate.
- e. tonicity — the degree of distention of the erythrocyte. This is dependent on the osmotic pressure of the cell's contents compared with that of the plasma. If it is greater, water will pass into the cell and it may rupture. If it is less, water passes out of the cell which shrinks and becomes crenated.
- e. volume — mean corpuscular volume (mcv); see erythrocyte indices (above).
