Bone marrow (sternum)
Medulla ossium rubra (sterni)
Lymphatic & immuneLymphaticsThorax
- What it is
- The red, blood-forming marrow filling the spongy interior of the breastbone, shown here as a slab inside the manubrium and body of the sternum. In adults red marrow survives only in the flat bones (sternum, ribs, pelvis, skull), the vertebrae and the upper ends of the femur and humerus.
- Function
- Makes all blood cells, about 500 billion a day, including the B lymphocytes that mature here and the T-cell precursors sent to the thymus.
- Size
- Slab about 15 cm long, 2-5 cm wide and 5 mm thick; the body holds about 2.6 kg of marrow, half of it red
- Clinical note
- The sternum is a classic site for marrow aspiration with a needle (the posterior iliac crest is now preferred), and its marrow is what a bone-marrow transplant replaces after high-dose chemotherapy.