Figure: Compact bone histology showing Haversian systems — Wikimedia Commons
Labelled Structures in Compact Bone Histology
| Label | Structure | Description |
|---|---|---|
| 1 | Haversian canal (central canal) | Central hollow channel containing blood capillaries and nerve fibres; runs longitudinally through the osteon |
| 2 | Lamellae | Concentric rings of calcified bone matrix (collagen + hydroxyapatite) arranged around the canal |
| 3 | Lacunae | Small oval spaces between lamellae housing osteocytes |
| 4 | Osteocytes | Mature bone cells trapped in lacunae; maintain bone matrix |
| 5 | Canaliculi | Tiny radiating channels connecting each lacuna to adjacent lacunae and to the central canal; contain cytoplasmic extensions of osteocytes |
| 6 | Osteon (Haversian system) | Entire concentric unit = lamellae + canal + lacunae + canaliculi |
| 7 | Periosteum | Outer fibrous covering of bone |
| 8 | Volkmann's canal | Transverse/oblique channels connecting Haversian canals to each other and to the periosteum |
Key Identification Features for NEET
- Concentric rings + central canal = ALWAYS bone (never cartilage)
- Osteocytes in lacunae = bone cells (contrast: chondrocytes in lacunae = cartilage)
- NEET 2020 tested this diagram directly