Microscopic Features of Bone
Compact bone is composed of repeating units of osteons with each unit having a central Haversian
canal. The central canal contains blood vessels, lymphatic vessels, and nerves that serve the compact
bone tissue, they travel from the periosteum to the central canal through perforating (Volkamann)
canals. These canals run horizontally in compact bone and connect with the central canal. The main
feature of each osteon is the concentric rings (lamellae). The dark areas are lacunae (house osteocytes)
and the thin lines are caniculi that connect osteocytes to the central canal. Interstitial lamellae fill in the
spaces between osteons.
Spongy bone does not contain osteons, but instead had trabeculae- flat plate with a lattice-like network
of thin, bony columns. The trabeculae has lamellae, lacunae, osteocytes, and caniculi. Spongy bone
has many spaces filled with red marrow. Blood vessels with in the red marrow provide the osteocytes
with nutrients. This fragile spongy bone needs the protection of an outer layer of compact bone.
1. Examine a prepared slide of ground compact bone. Under low poer identify an osteon, central
haversian canal, concentric lamellae, and interstitial lamellae. Count the number of osteons in
one field of view.
2. Under high power, identify the caniculi and lacunae.
3. Examine a prepared slide of spongy (cancellous) bone. Under low power identify the trabeculae.
4. Under high power, identify the lacunae (darker areas in the trabeculae)
5. Go to www.wiley.com/college/allen to observe osteoblasts, osteoclasts, and bone formation.
1. What do compact and spongy bone have in common? How do they differ?
2. Relate the structure of compact bone to its function.
3. Relate the structure of spongy bone to its function.
4. Identify structures in the diagram and micrograph below.