bone marrow(redirected from Myeloic tissue)
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bone marrow,soft tissue filling the spongy interiors of animal bones. Red marrow is the principal organ that forms blood cells in mammals, including humans (see bloodblood,
fluid pumped by the heart that circulates throughout the body via the arteries, veins, and capillaries (see circulatory system; heart). An adult male of average size normally has about 6 quarts (5.6 liters) of blood.
..... Click the link for more information. ). In children, the bones contain only red marrow. As the skeleton matures, fat-storing yellow marrow displaces red marrow in the shafts of the long bones of the limbs. In adults red marrow remains chiefly in the ribs, the vertebrae, the pelvic bones, and the skull. Erythrocytes (red blood cells), platelets, and all but one kind of leukocyte (white blood cell) are manufactured in human red marrow. The marrow releases about 10 million to 15 million new erythrocytes every second, while an equivalent number are destroyed by the spleen.
Diseases of the marrow, such as leukemialeukemia
, cancerous disorder of the blood-forming tissues (bone marrow, lymphatics, liver, spleen) characterized by excessive production of immature or mature leukocytes (white blood cells; see blood) and consequently a crowding-out of red blood cells and platelets.
..... Click the link for more information. or multiple myeloma, or injury to it from metallic poisons can interfere with the production of erythrocytes, causing anemiaanemia
, condition in which the concentration of hemoglobin in the circulating blood is below normal. Such a condition is caused by a deficient number of erythrocytes (red blood cells), an abnormally low level of hemoglobin in the individual cells, or both these conditions
..... Click the link for more information. . A bone marrow biopsy, in which a small sample of bone marrow is obtained by aspiration through a thin needle, may be used to aid in the diagnosis of leukemia, anemia, and other blood disorders, as well as to gain insight on the normal functioning of the cells of the bone marrow.
Bone marrow transplantation is a technique that infuses healthy bone marrow into a patient whose bone marrow is defective. The transplant can be autologous, consisting of bone marrow removed from the patient, treated, and then reinserted, or it can be allogeneic, consisting of healthy bone marrow obtained from a closely related donor, such as a sibling (see transplantation, medicaltransplantation, medical,
surgical procedure by which a tissue or organ is removed and replaced by a corresponding part, usually from another part of the body or from another individual.
..... Click the link for more information. ). Bone marrow transplants are most frequently undergone for leukemia, severe forms of anemia, and disorders of the immune system. The major complications are graft-versus-host disease (as a result of allogeneic transplantation) and infections that occur before the transplanted marrow begins to produce leukocytes.
the tissue that fills the cavities of the bones in vertebrate animals and man. A distinction is made between red marrow, with a predominance of hematopoietic myeloid tissue, and yellow marrow, with a predominance of fatty tissue. Red marrow remains throughout life in the flat bones (ribs, sternum, and cranial and pelvic bones) and in the vertebrae and epiphyses of the long bones. In man, bone marrow constitutes approximately 1.5 percent of the body mass. The hematopoietic tissue in the cavities of the long bones is eventually replaced by fatty tissue and the marrow becomes yellow.
Red bone marrow is the main hematopoietic organ in man and other adult mammals. The red blood cells, granular leukocytes (neutrophils, eosinophils, basophils), blood platelets (thrombocytes), and marrow lymphocytes are produced by the red bone marrow. Bone marrow contains hematopoietic stem cells (approximately 0.1 percent of all its cells). Owing to their capacity for repeated division and development into all forms of hematopoietic and lymphoid cells, stem cells sustain hematopoiesis in the bone marrow and replace the white and red blood cells that are constantly being destroyed in the body. Bone marrow primarily consists of different series of maturing cells (erythroid, myeloid, lymphocytic megakaryocytic). All are produced and replenished by the stem cells, and some are capable of repeated division. The relative amount of maturing cells of the individual blood series and of more or less mature cellular forms of each series in bone marrow is an important characteristic of hematopoiesis. As the cells from the bone marrow mature, they enter the bloodstream. In addition to mature cells, some hematopoietic stem cells emerge from the bone marrow and migrate to other hematopoietic organs. The basis of bone marrow is reticular tissue, which forms the syncytium, in which the hematopoietic cells are distributed. The multiplication and maturation of these cells are largely dependent on their interaction with reticular tissue (which is also capable of forming bone, a phenomenon manifested during the healing of bone fractures). The rate of hematopoiesis in bone marrow can increase sharply. As a result, a substantial loss of blood cells (for example, in bleeding) or the destruction of many bone marrow cells is usually compensated for quickly. However, bone marrow (especially its stem cells) is highly sensitive to certain agents (for example, ionizing radiation). Therefore, the condition of bone marrow is one of the principal factors determining the body’s resistance to such agents.
REFERENCESZavarzin, A. A., and A. V. Rumiantsev. Kurs gistologii, 6th ed. Moscow, 1946.
Chertkov, I. L., and A. la. Fridenshtein. “Rodonachal’naia krovetvornaia kletka i ee differentsirovka.” Uspekhi sovremennoi biologii, 1966, vol. 62, no. 1.
A. IA. FRIDENSHTEIN