: 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 the long bones—called also yellow marrowb: a reddish bone marrow containing little fat, being the chief seat of red blood cell and blood granulocyte formation, and occurring in the normal adult only in cancellous tissue especially in certain flat bones—called also red marrow
Soft, gelatinous tissue that fills bone cavities. Red bone marrow contains stem cells, progenitor cells, percursor cells, and functional blood cells (seereticuloendothelial system). Lymphocytes mature in the lymphoid organs (seelymphoid 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.