Microscopically, spongy bone is composed of tree trunk-shaped repeating units called:

Spongy bone is not primarily composed of osteons or Haversian systems, which are characteristic features of compact bone. Instead, spongy bone consists of a network of trabeculae, which are thin, rod-like structures that provide structural support while maintaining lightweight properties.

Osteons, also known as Haversian systems, are cylindrical structures that are specifically found in compact bone. They serve to organize the dense matrix of compact bone, accommodating blood vessels and nerves. The confusion might arise because both terms relate to bone structure, but they pertain to different types of bone.

In summary, the correct understanding is that spongy bone's architecture is fundamentally different from that of compact bone, focusing more on the trabecular organization rather than on the repeating units found in osteons or Haversian systems. This distinction is crucial in understanding the structural differences and functional roles of various types of bone within the skeletal system.