Bone Marrow

Bone marrow ( Latin : medulla ossium ) is the flexible tissue found in the interior of bones . In humans , bone marrow in large bones produces new blood cells . On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg (143 lbs), bone marrow accounts for approximately 2.6 kg (5.7 lbs). The hematopoietic compartment of bone marrow produces approximately 500 billion blood cells per day, which use the bone marrow vasculature as a conduit to the body's systemic circulation.
[ 1 ] Bone marrow is also a key component of the lymphatic system , producing the lymphocytes that support the body's immune system .