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There are two types of marrow, red and yellow. The former produces the blood cells; the latter, which is mainly formed of fatty tissue, normally has no blood-producing function. During infancy and early childhood all bone marrow is red. But gradually, as one gets older and less blood cell production is needed, the fat content of the marrow increases as some of it turns from red to yellow. Red marrow is present in adulthood only in the flat bones of the skull, the sternum, ribs, vertebral column, clavicle, humerus, and part of the femur. However, under certain conditions, as after hemorrhage, yellow marrow in other bones may again be converted to red and resume its cell-producing functions.
The marrow is occasionally subject to disease, as in aplastic anemia, which may be caused by destruction of the marrow by chemical agents or excessive x-ray exposure. Other diseases that affect the bone marrow are leukemia, pernicious anemia, myeloma, and metastatic tumors.
See also: medulla.
See also: medulla.
marrow/mar·row/ (mar´o) bone marrow; the soft organic material filling the cavities of bones, made up of a fiber-rich meshwork of connective tissue, the meshes being filled with marrow cells, which consist variously of fat cells, large nucleated cells or myelocytes, and megakaryocytes. Yellow bone m. is that in which fat cells predominate; red bone m. is the site of production of erythrocytes and granular leukocytes and occurs in developing bone, as of the ribs and vertebrae.
marrow(1) Bone marrow, see there.
(2) Reactive marrow.
See also: medulla
bone marrowMarrow (1).
spinal marrowMarrow (2).illustration
marrowthe pulp-like content of the cavities of larger bones that produces red and sometimes white blood corpuscles.
Patient discussion about marrow
Q. What is a bone marrow transplant? I wanted to enter myself as a potential bone marrow donor and wanted to know first of all what bone marrow is? What does a bone marrow transplant mean and how is it done?
Q. What is Leukemia? My brother's best friend has been diagnosed with Leukemia. What is it? Is it dangerous? Can you recover from it?