- bone marrow
marrow1 (def. 1).
* * *or myeloid tissueSoft, gelatinous tissue that fills bone cavities.Red bone marrow contains stem cells, progenitor cells, percursor cells, and functional blood cells (see reticuloendothelial system). Lymphocytes mature in the lymphoid organs (see lymphoid tissue). All other blood-cell formation occurs in red marrow, which also takes part in destruction of old erythrocytes (red blood cells). Yellow bone marrow mainly stores fats. Because the leukocytes (white blood cells) produced in bone marrow are involved in immune defenses, marrow transplants can treat some types of immunodeficiency. Radiation and some anticancer drugs can damage marrow and impair immunity. Bone-marrow examination helps diagnose diseases related to blood and blood-forming organs.
* * *▪ anatomyalso called myeloid tissuesoft, gelatinous tissue that fills the cavities of the bones (bone). Bone marrow is either red or yellow, depending upon the preponderance of hematopoietic (red) or fatty (yellow) tissue. In humans the red bone marrow forms all of the blood cells with the exception of the lymphocytes (lymphocyte), which are produced in the marrow and reach their mature form in the lymphoid organs. Red bone marrow also contributes, along with the liver and spleen, to the destruction of old red blood cells. Yellow bone marrow serves primarily as a storehouse for fats but may be converted to red marrow under certain conditions, such as severe blood loss or fever. At birth and until about the age of seven, all human marrow is red, as the need for new blood formation is high. Thereafter, fat tissue gradually replaces the red marrow, which in adults is found only in the vertebrae, hips, breastbone, ribs, and skull and at the ends of the long bones of the arm and leg; other cancellous, or spongy, bones and the central cavities of the long bones are filled with yellow marrow.Red marrow consists of a delicate, highly vascular fibrous tissue containing stem cells (stem cell), which differentiate into various blood cells. Stem cells first become precursors, or blast cells, of various kinds; normoblasts give rise to the red blood cells (erythrocytes (erythrocyte)), and myeloblasts become the granulocytes, a type of white blood cell ( leukocyte). Platelets (platelet), small blood cell fragments involved in clotting, form from giant marrow cells called megakaryocytes. The new blood cells are released into the sinusoids, large thin-walled vessels that drain into the veins of the bone. In mammals, blood formation in adults takes place predominantly in the marrow. In lower vertebrates a number of other tissues may also produce blood cells, including the liver and the spleen.Because the white blood cells produced in the bone marrow are involved in the body's immune defenses, marrow transplants have been used to treat certain types of immune deficiency and hematological disorders, especially leukemia. The sensitivity of marrow to damage by radiation therapy and some anticancer drugs accounts for the tendency of these treatments to impair immunity and blood production.Examination of the bone marrow is helpful in diagnosing certain diseases, especially those related to blood and blood-forming organs, because it provides information on iron stores and blood production. bone marrow aspiration, the direct removal of a small amount (about 1 ml) of bone marrow, is accomplished by suction through a hollow needle. The needle is usually inserted into the hip or sternum (breastbone) in adults and into the upper part of the tibia (the larger bone of the lower leg) in children. The necessity for a bone marrow aspiration is ordinarily based on previous blood studies and is particularly useful in providing information on various stages of immature blood cells. Disorders in which bone marrow examination is of special diagnostic value include leukemia, multiple myeloma, Gaucher disease, unusual cases of anemia, and other hematological diseases.
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Bone marrow — Simplified illustration of cells in bone marrow. Latin medulla ossium Code TA … Wikipedia
bone marrow — n a soft highly vascular modified connective tissue that occupies the cavities and cancellous part of most bones and occurs in two forms: a) a whitish or yellowish bone marrow consisting chiefly of fat cells and predominating in the cavities of… … Medical dictionary
bone marrow — bone .marrow n [U] the soft substance in the hollow centre of bones = ↑marrow ▪ a bone marrow transplant … Dictionary of contemporary English
bone marrow — marrow the tissue contained within the internal cavities of the bones. At birth, these cavities are filled entirely with blood forming myeloid tissue (red marrow) but in later life the marrow in the limb bones is replaced by fat (yellow marrow).… … The new mediacal dictionary
bone marrow — bone ,marrow noun uncount the soft substance inside bones … Usage of the words and phrases in modern English
bone marrow — noun 1. the fatty network of connective tissue that fills the cavities of bones (Freq. 2) • Syn: ↑marrow • Hypernyms: ↑connective tissue • Hyponyms: ↑red marrow, ↑red bone marrow, ↑ … Useful english dictionary
bone marrow — N UNCOUNT Bone marrow is the soft fatty substance inside human or animal bones. There are 2,000 children worldwide who need a bone marrow transplant. Syn: marrow … English dictionary
bone marrow — noun the soft substance in the hollow centre of bones; marrow (1): a bone marrow transplant … Longman dictionary of contemporary English
bone marrow — noun Bone marrow is used before these nouns: ↑donor, ↑transplant … Collocations dictionary
bone marrow — noun Date: 1893 a soft highly vascular modified connective tissue that occupies the cavities of most bones and occurs in two forms: a. one that is yellowish, consists chiefly of fat cells, and is found especially in the cavities of long bones b.… … New Collegiate Dictionary