marrow
Long bones are longer than they are wide and have a shaft and two ends. The diaphysis, or central shaft, contains bone marrow in a marrow cavity. The rounded ends, the epiphyses, are covered with articular cartilage and are filled with red bone marrow, which produces blood cells Figure 38.17 . Most of the limb bones are long bonesfor example, the femur, tibia, ulna, and radius. Exceptions to this include the patella and the bones of the wrist and ankle.