Megakaryocyte: An extremely large cell with an irregular lobed, ring or doughnut-
shaped nucleus that stains blue-purple. The cytoplasm is abundant, light blue and is
packed with fine azurophilic granules. This cell gives rise to thrombocytes.
Megaloblast: The type of red cell precursor found in pernicious anemia. This differs
from the normal erythrocyte precursor (normoblast) in that the megaloblast is larger and
the nuclear chromatin has a fine meshwork or scroll design.
M.E. Ratio: The ratio of myeloid to erythroid cells in the bone marrow.
Mesentery: The fold of peritoneum that attaches the intestine to the posterior
Metamyelocyte: Juvenile cell of Schilling.
Metarubricyte: An erythrocyte with a pyknotic, contracted nucleus. Also called
Methemoglobin: A spectroscopically detected compound of hemoglobin found in
nitrobenzol, and other poisonings. The blood is a chocolate brC1.oln color to the eye.
Microcyte: An erythrocyte smaller than normal.
Microcytosis: An increase in the number of microcytes
Micron: One-thousandth of a millimeter, the common unit of microscopic measure.
Mitochondria: Granular components of a cell cytoplasm active in oxidative processes.
Mitosis: A series of changes through which the nucleus passes in indirect cell division.
A tissue showing many cells in mitosis indicates rapid gro.&1th of that tissue.
Monoblast: The parent cell of the monocytic series.
Monocyte: A large white blood cell with a pale blue-gray cytoplasm containing fine
azurophilic granules. The nucleus is spongy and lobulated.
Monocytosis: A relative or absolute increase in the number of circulating monocytes.
Mucosa: Mucous membrane.
Myeloblast: The parent cell of the granulocytic or myelocytic series.
Myelocyte: The stage in development of the granulocytic series that is characterized
by the first appearance of specific granules (eosinophilic, neutrophilic or basophilic) and
a round nucleus.