where is the bone marrow located in the body
Bone marrow Bone marrow is a semi-solid tissue which may be found within the spongy or cancellous portions of bones.[2] In birds and mammals, bone marrow is the primary site of new blood cell production or hematopoiesis.[3] It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells. On average, bone marrow constitutes 4% of the total body mass of humans; in an adult having 65 kilograms of mass (143 lb), bone marrow typically accounts for approximately 2.6 kilograms (5.7 lb).[4] Human marrow produces approximately 500 billion blood cells per day, which join the systemic circulation via permeable vasculature sinusoids within the medullary cavity.[5] All types of hematopoietic cells, including both myeloid and lymphoid lineages, are created in bone marrow; however, lymphoid cells must migrate to other lymphoid organs (e.g. thymus) in order to complete maturation.