A nucleated red blood cell (NRBC), also known by several other names, is a red blood cell that contains a cell nucleus. Almost all vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of these red blood cells are nucleated. In mammals, NRBCs occur in normal development as precursors to mature red blood cells in erythropoiesis, the process by which the body produces red blood cells.
A human peripheral blood smear; NRBCs are visible as larger cells with dark centers.
Normocyte, Giemsa stain
Blood cell lineage
Image: Prorubricyte
Red blood cells (RBCs), scientific name erythrocytes (from ancient Greek erythros 'red' and kytos 'hollow vessel', with -cyte translated as 'cell' in modern usage), also known as red cells, erythroid cells, and rarely haematids, are the most common type of blood cell and the vertebrate's principal means of delivering oxygen (O2) to the body tissues—via blood flow through the circulatory system. Erythrocytes take up oxygen in the lungs, or in fish the gills, and release it into tissues while squeezing through the body's capillaries.
There is an immense size variation in vertebrate red blood cells, as well as a correlation between cell and nucleus size. Mammalian red blood cells, which do not contain nuclei, are considerably smaller than those of most other vertebrates.
Mature red blood cells of birds have a nucleus, however in the blood of adult females of penguin Pygoscelis papua enucleated red blood cells (B) have been observed, but with very low frequency.
Scanning electron micrograph of blood cells. From left to right: human red blood cell, thrombocyte (platelet), leukocyte.
Two drops of blood are shown with a bright red oxygenated drop on the left and a darker red deoxygenated drop on the right.
