Anatomy and Physiology / Unit 4: The Skeletal System
4.2 Bone Structure and Tissue
Notes
A long bone has a diaphysis (shaft), two epiphyses (ends covered with articular cartilage), and metaphyses where they meet (the growth plate region in children).
- The periosteum is the tough outer membrane (with blood vessels and nerves); the endosteum lines the marrow cavity. The medullary cavity holds yellow marrow in adults.
- Compact bone is dense and smooth, made of units called osteons (Haversian systems) with a central canal. Spongy (cancellous) bone has a lattice of trabeculae with red marrow, found in the epiphyses and in flat bones.
- Cells: osteoblasts build bone, osteocytes are mature cells maintaining it, osteoclasts break down (resorb) bone. The matrix is about two-thirds mineral (calcium phosphate) for hardness and one-third collagen for flexibility.
Practice
Which cell type breaks down bone matrix and releases calcium?
Osteoclasts resorb bone. Osteoblasts build it.
The shaft of a long bone is the:
The diaphysis is the long central shaft.
The collagen in bone matrix mainly provides:
Collagen resists stretching and twisting. Minerals provide hardness.
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