Which statements characterize the microscopic arrangement of spongy bone? ? it contains parallel lamellae ? it contains concentric lamellae ? it contains no osteons ? it contains many osteons
The Correct Answer and Explanation is:
Correct Answers:
- ✅ It contains parallel lamellae
- ✅ It contains no osteons
Explanation:
Spongy bone, also known as cancellous bone or trabecular bone, differs significantly from compact bone in both structure and function. Microscopically, it is characterized by a lattice-like network of trabeculae—thin plates or struts of bone—that create a porous architecture. This arrangement helps reduce bone weight while still providing structural support.
1. Parallel Lamellae
In spongy bone, lamellae (layers of bone matrix) are organized in a more irregular and parallel fashion within trabeculae. Unlike compact bone, which has a highly ordered structure, spongy bone’s lamellae follow the orientation of trabeculae and are not concentric. The bone cells (osteocytes) lie within lacunae between these lamellae and communicate via canaliculi.
2. No Osteons
Osteons (or Haversian systems) are the fundamental structural units of compact bone, where concentric lamellae surround a central Haversian canal containing blood vessels and nerves. Spongy bone lacks osteons. Instead, the trabeculae are thin enough to allow diffusion of nutrients from the surrounding bone marrow, making the central canal system unnecessary.
3. Not Concentric Lamellae
Because spongy bone lacks osteons, it also lacks concentric lamellae, which are exclusive to compact bone. This reinforces the idea that the bone matrix in spongy bone is organized differently.
4. Not Many Osteons
Spongy bone contains no osteons, let alone “many.” That description applies to compact bone, which is dense and built from numerous osteons stacked tightly together.
In summary, the microscopic architecture of spongy bone is adapted for lightness and metabolic activity rather than mechanical strength, which is the role of compact bone. Hence, it is defined by parallel lamellae and no osteons.
