- Also called:
- myeloid tissue
- Key People:
- Siddhartha Mukherjee
- E. Donnall Thomas
bone marrow
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What is bone marrow?
Bone marrow is a soft, gelatinous tissue filling bone cavities. It exists in two forms: red and yellow. Red marrow produces blood cells, except for lymphocytes, which mature in lymphoid organs. It also helps break down old red blood cells, along with the liver and spleen.
Yellow marrow primarily stores fat but can convert to red marrow during blood loss or fever. At birth, all marrow is red, but it gradually turns to yellow with age. In adults, red marrow is mainly in the vertebrae, hips, breastbone, ribs, skull, and ends of arm and leg bones. Examination of bone marrow helps diagnose blood-related diseases. Marrow transplants treat immune deficiencies and hematological disorders like leukemia.
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Where is bone marrow found in the body?
Bone marrow is a soft, gelatinous tissue within bone cavities. There are two types: red and yellow. Red marrow produces blood cells, except for lymphocytes, which mature in lymphoid organs. It also helps break down old red blood cells, along with the liver and spleen.
At birth, all marrow is red but, with age, fat tissue replaces it. In adults, red marrow is primarily in the vertebrae, hips, breastbone, ribs, skull, and at the ends of the arm and leg bones. Yellow marrow, mainly a fat store, fills other spongy bones and the central cavities of long bones but can revert to red marrow if needed.
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What are the two main types of bone marrow?
Bone marrow, a soft tissue filling bone cavities, exists in two primary forms: red and yellow bone marrow.
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Red marrow is the site of blood cell formation, producing red blood cells, white blood cells, and platelets. It also helps to destroy old red blood cells.
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Yellow marrow consists mainly of fat cells and can convert to red marrow under certain conditions, such as severe blood loss.
At birth, all marrow is red, but with age, fat tissue replaces red marrow, which in adults is primarily in the vertebrae, hips, breastbone, ribs, and skull.
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What is the main function of bone marrow?
Bone marrow, found inside bones, has two types: red and yellow. Red bone marrow's primary function is to produce blood cells. It creates red blood cells, platelets, and most white blood cells, all essential for oxygen transport, clotting, and immunity. Yellow bone marrow mainly stores fat but can convert to red marrow if severe blood loss or fever occurs. Bone marrow also helps to eliminate old red blood cells. Examination of the bone marrow can help in diagnosing diseases, especially those related to blood and blood-forming organs.
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How does bone marrow produce blood cells?
Bone marrow, a soft tissue within bones, is the primary site of blood cell production in adults. This process, called hematopoiesis, involves stem cells differentiating into various blood cells. Red marrow contains stem cells that become precursors, or blast cells, of different kinds. Normoblasts give rise to red blood cells, and myeloblasts become granulocytes, a type of white blood cell. Platelets, which are small blood cell fragments involved in clotting, form from giant marrow cells called megakaryocytes. The new blood cells are then released into the sinusoids, large, thin-walled vessels that drain into the veins of the bone.
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How can diseases affect bone marrow and its function?
Bone marrow, found in bones, is crucial for producing blood cells. Diseases can significantly impair its function:
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Aplastic anemia causes the bone marrow to fail, resulting in a reduced production of all blood cells.
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Leukemia, a cancer of the blood-forming tissues, including bone marrow, disrupts normal blood cell production. Genetic mutations in bone marrow cells can result in different types of leukemia.
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Infections, tumors, and certain drugs or radiation can also damage the bone marrow, leading to a failure in red blood cell production and anemia.
Bone marrow diseases can be treated with bone marrow transplants, which replace damaged or diseased marrow with healthy marrow from a donor.
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bone marrow, soft, gelatinous tissue that fills the cavities of the bones. 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, 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, 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), and myeloblasts become the granulocytes, a type of white blood cell (leukocyte). Platelets, 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.
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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.