There are two types of bone marrow: red marrow (also known as myeloid tissue) and yellow marrow. Red blood cells, platelets and most white blood cells arise in red marrow; some white blood cells develop in yellow marrow. The color of yellow marrow is due to the much higher number of fat cells. Both types of bone marrow contain numerous blood vessels and capillaries.
At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type. Adults have on average about 2.6 kg (5.7 lbs.) of bone marrow, with about half of it being red. Red marrow is found mainly in the flat bones, such as the hip bone, breast bone, skull, ribs, vertebrae and shoulder blades, and in the cancellous ("spongy") material at the proximal ends of the long bones femur and humerus. Yellow marrow is found in the hollow interior of the middle portion of long bones.
In cases of severe blood loss, the body can convert yellow marrow back to red marrow in order to increase blood cell production.
2007-12-20 13:14:14
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answer #2
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answered by bob 6
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