Bone marrow

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The bone marrow (medulla ossium) is a hemopoietic organ from the 7th month of the prenatal period (the so-called medullo-lymphatic period). It is found in the bodies of long bones and in the spaces between the trabeculae of spongiosa. It fills the medullary cavity (cavitas medullaris). A soft, macroscopically diverse tissue composed of reticular tissue. A sternal puncture is obtained for microscopic examination.

Medulla ossium rubra = red bone marrow
It is a hematopoietic organ. It consists of a spatial network of reticular tissue (reticular cells, fibers), macrophages and wide blood capillaries. There are stem cells for the formation of erythrocytes, most leukocytes and platelets in the meshes of the ligament. Red bone marrow remains in the spongiosa of the articular ends of long bones, in the spongiosa of short bones, in the pelvic bones, in the sternum, ribs, and in the diploe of the cranial bones.

 Contains:
 * reticular cells - form a network in which stem cells are located;
 * fat cells - their quantity can change depending on the need for blood formation;
 * macrophages'
 * phagocytose apoptotic immature blood cells and old erythrocytes
 * participate in the control of hemopoiesis by releasing factors

Medulla ossium flava = yellow bone marrow
It arises from red bone marrow. In the marrow of long bones, hematopoiesis ceases during growth, the reticular ligament is penetrated by fat cells, and the red marrow turns yellow. By age 20, yellow bone marrow is in the cavities of all long bones (exception - the proximal end of the body of the humerus and femur). It is capable of reactivation to red bone marrow.

Medulla ossium grisea = gray bone marrow
It is translucent and arises from the yellow pulp through the loss of fat. It is typical for late age.

Related Articles

 * Blood
 * Punch (bone marrow sampling)