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The five major categories of leukocytes in mammals are neutrophils, eosinophils,
basophils, lymphocytes, and monocytes. The first three collectively are called granulocytes,
because they contain granules in their cytoplasm, and the latter two collectively are called
mononuclear cells in reference to their round nuclei. These collective terms are somewhat
misleading since some granulocytes have barely perceptible granules and most monocytes
do not have round nuclei. Granulocytes of most mammals are classed as neutrophil,
eosinophil, and basophil based on the reaction of their specific granules with the dyes in
polychrome blood stains, called Romanowsky stains.
The prototype species for granulocyte classification is human, in which neutrophil granules are small and pink with weak affinity for azure complexes, basophil granules are deep purple because of strong affinity for the azure complexes, and eosinophils are intensely orange because of strong binding of eosin. Classification of granulocytes in animal species is based in part on homology of appearance to human granulocytes and in part on demonstration of homology of enzyme content and function. There are many differences, some subtle and some obvious, among species and within species. This portion of the module presents the identifying features of leukocytes in several animal species and illustrates the species differences. Continue by working through the following topics: |
[ Neutrophils ] [ Lymphocytes ] [ Monocytes ] [ Eosinophils ] [ Basophils]
Last Updated on Monday, January 08, 1996