bone marrow

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 the long bones called also yellow marrow

b) 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 esp. in certain flat bones called also red marrow

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(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). Samples of bone marrow may be obtained for examination by aspiration through a stout needle or by trephine biopsy. See also haemopoiesis.

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medulla ossium.