Normal bone marrow has yellow marrow and red marrow. Yellow marrow is more of fat and red marrow is more of haematopoitic tissue. in infants marrow is predominantly hematopoietic with the exception of epiphyses & apophyses, which are predominantly fatty throughout life. with skeletal growth, red marrow is gradually replaced by fat. red marrow persistis longer in the vertebrae, pelvic bones, sternum, & proximal ends of the long tubular bones, during normal marrow conversion, residual islands of red marrow may subsist in the yellow marrow, as may fatty foci in red marrow.islands of red marrow residue may be a normal variant especially in obese women, cigarette smokers, marathon runners. It may be pathological some times in cases of hemolytic processes / anemia.
Thanks for the explanation. Being that I am not smoker, not a marathon runner and have never been told I was anemic should I be concerned?