Answer
Spongy ( cancellous) bone contains red bone marrow which is the erythropoietic tissue of the body. The matrix exists as irregular spikes and trabeculae ; it is not arranged in cylindrical osteons (Haversian canal units) as in compact bone.
Work Step by Step
Long bones like the femur ( thigh bone) and the tibia and fibula ( leg bones) consist mainly of compact bone in adults. There is spongy bone at the epiphyses (ends) of these bones but the diaphysis --long middle segment of the bone- is composed of compact bone.
Spongy bone is lighter than the more dense compact bone; nevertheless, the former is not weaker , structurally, than the latter, because the architectural arrangements of the spikes, struts, and trabeculae of cancellous bone give it great strength.
