Veterinary Histology and Embryology

BONE MARROW

This is a soft tissue which occupies the medullary cavity of the long bones and the space between trabeculae of spongy bone. It consists of a delicate reticular connective tissue in the meshes of which are many kinds of cells.

• Two varieties of marrow are seen, red and yellow.
  • Red marrow:
    • It is the only type found in foetal and young bones, but in the adult it is restricted to the vertebrae, sternum, ribs, cranial bones and the epiphyses of long bones. It is the chief blood forming organ of the adult body being the normal source of the red blood corpuscles and granular leucocytes.
  • Yellow marrow:
    • Consists of mainly fat cells which have gradually replaced the other marrow elements.