Structure of a Long Bone
![Diagram showing a detailed cross-section of a long bone, highlighting periosteum, compact bone, spongy bone, yellow marrow, red marrow, blood vessels, and epiphyseal plate/line]
Key Components of a Long Bone
1. Diaphysis (Shaft)
- The long, cylindrical main body of the bone
- Made primarily of compact (cortical) bone
- Contains the medullary cavity filled with yellow marrow
- Surrounded by periosteum (outer membrane)
2. Epiphyses (Ends)
- The expanded ends of the long bone
- Covered with articular cartilage
- Contains red marrow within spongy bone
- Usually where joints form with other bones
Remember that epiphyses is plural (multiple ends) while epiphysis is singular (one end)!
3. Bone Structure Layers
Outer Layer (Periosteum)
- Double-layered membrane covering the bone
- Contains blood vessels and nerves
- Essential for bone growth and repair
- Anchors tendons and ligaments
Compact Bone
- Dense, solid bone tissue
- Organized in osteons (Haversian systems)
- Provides strength and protection
- Contains small channels for blood vessels and nerves
Spongy Bone (Trabecular)
- Lightweight, honeycomb structure
- Found mainly in epiphyses
- Contains red marrow between trabeculae
