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soft spongy material; called also medulla. The term is often restricted to mean bone marrow.
bone marrow the soft, organic, spongelike material in the cavities of bones; called also medulla ossium. It is a network of blood vessels and special connective tissue fibers that hold together a composite of fat and blood-producing cells. Its chief function is to manufacture erythrocytes, leukocytes, and platelets. These blood cells normally do not enter the bloodstream until they are fully developed, so that the marrow contains cells in all stages of growth. If the body's demand for leukocytes is increased because of infection, the marrow responds immediately by stepping up production. The same is true if more erythrocytes are needed, as in hemorrhage or anemia.

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.
Cells of the bone marrow and the blood. From Malarkey and McMorrow, 2000.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


(ma'rō), [TA]
1. A highly cellular hemopoietic connective tissue filling the medullary cavities and spongy epiphyses of bones; it becomes predominantly fatty with age, particularly in the long bones of the limbs.
See also: medulla.
2. Any soft gelatinous or fatty material resembling the marrow of bone.
See also: medulla.
[A.S. mearh]
Farlex Partner Medical Dictionary © Farlex 2012


1. Bone marrow.
2. The spinal cord.

mar′row·y adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


(1) Bone marrow, see there. 
(2) Reactive marrow.
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


(ma'rō) [TA]
1. A highly cellular hematopoietic connective tissue filling the medullary cavities and spongy epiphyses of bones that becomes predominantly fatty with age, particularly in the long bones of the limbs.
2. Any soft gelatinous or fatty material resembling the marrow of bone.
See also: medulla
[A.S. mearh]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


Enlarge picture
RED BONE MARROW: Red bone marrow can only be found in the ribs, sternum, vertebrae, skull, pelvis, and upper parts of both the humerus and femur. All other bones contain yellow marrow.
1. The soft tissue in the marrow cavities of long bones (yellow marrow) and in the spaces between trabeculae of spongy bone in the sternum and other flat and irregular bones (red marrow). Yellow marrow consists principally of fat cells and connective tissue and does not participate in hematopoiesis. Red marrow produces redf blood cells. Synonym: bone marrow; medulla (1) See: illustration
2. The substance of the spinal cord. Synonym: spinal marrow

bone marrow

Marrow (1).

gelatinous marrow

Yellow marrow of the old or the emaciated, almost devoid of fat and having a gelatinous consistency.

spinal marrow

Marrow (2).illustration
Medical Dictionary, © 2009 Farlex and Partners


the pulp-like content of the cavities of larger bones that produces red and sometimes white blood corpuscles.
Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005

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?

A. Bone marrow is a soft, fatty tissue inside the bones. This is where blood cells are produced, and where they develop. Transplanted bone marrow will restore production of white blood cells, red blood cells, and platelets. Donated bone marrow must match the patient's tissue type. It can be taken from the patient, a living relative (usually a brother or a sister), or from an unrelated donor. Donors are matched through special blood tests called HLA tissue typing. Bone marrow is taken from the donor in the operating room while the donor is unconscious and pain-free (under general anesthesia). Some of the donor's bone marrow is removed from the top of the hip bone. The bone marrow is filtered, treated, and transplanted immediately or frozen and stored for later use. Transplant marrow is transfused into the patient through a vein (IV) and is naturally carried into the bone cavities where it grows to replace the old bone marrow.

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?

A. Leukemia is the general name for four different types of blood cancers. In people with leukemia, the bone marrow produces abnormal white blood cells. The abnormal cells are leukemia cells. At first, leukemia cells function almost normally. In time, they may crowd out normal white blood cells, red blood cells, and platelets. This makes it hard for blood to do its work. After diagnosis, many people with leukemia do survive and live many good, quality years. The relative five-year survival rate has more than tripled in the past 47 years for patients with leukemia. In 1960-63, when compared to a person without leukemia, a patient had a 14 percent chance of living five years. By 1975-77, the five year relative survival rate had jumped to 35 percent, and in 1996-2003 the overall relative survival rate was nearly 50 percent.

More discussions about marrow
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References in periodicals archive ?
Table 1: Cases diagnosed on bone marrow aspirate and trephine biopsy
of cases###Bone marrow aspirate###Bone marrow biopsy
###bone marrow aspirate cytology with trephine biopsy
The procedure is similar to that of a full- matched bone marrow transplant but more complicated.
Total of 83 newly diagnosed cases of neuroblastoma referred to our department for bone marrow biopsy were included in this study.
Table 1: Cytopenias in Patients with and Without Bone Marrow Neuroblastoma Infiltration.
There were two cases of stage 1V S infantile neuroblastoma with infiltration of liver, bone marrow and skin.
The prospect of undergoing a bone marrow procedure can create a significant degree of apprehension in patients.
This study highlights the use of the 1-needle technique to yield a bone marrow sample comparable to one obtained using traditional technique for bone marrow collection.
To our knowledge, this is the first systematic comparison study of multiple parameters of bone marrow biopsy specimens obtained by the traditional 2-needle technique versus the 1-needle technique for bone marrow collection.
Processes that either infiltrate or replace the bone marrow can also present as or result in an acquired pancytopenia.
Marrow fibrosis was seen in three cases, two cases had hepatosplenomegaly and extensive fibrosis in the third case was accompanied by infiltrates of lymphocytes and histiocytes.