As we grow, our long bones increase in diameter, but the thickness of the compact bone of the shaft remains relatively constant. Explain this phenomenon.

Verified step by step guidance

1. Understand that bone growth in diameter is known as appositional growth, which involves the addition of new bone tissue on the outer surface of the bone.
2. Recognize that osteoblasts, the bone-forming cells, are responsible for depositing new bone on the outer surface of the bone shaft, increasing its diameter.
3. Acknowledge that osteoclasts, the bone-resorbing cells, simultaneously remove bone from the inner surface of the bone shaft, which helps maintain the thickness of the compact bone.
4. Consider the balance between the activity of osteoblasts and osteoclasts, which ensures that while the bone grows in diameter, the compact bone does not become excessively thick or thin.
5. Realize that this coordinated activity allows the bone to grow in size while maintaining its structural integrity and strength, ensuring that the bone remains lightweight yet strong enough to support the body.

Key Concepts

Bone Growth and Remodeling

Bone growth occurs through a process called remodeling, where old bone tissue is replaced with new tissue. This process is regulated by various factors, including mechanical stress and hormonal signals. As long bones grow in length and diameter, the inner bone structure adapts to maintain strength while allowing for increased size.

Compact Bone Structure

Compact bone, also known as cortical bone, is dense and forms the outer layer of bones. It provides strength and support, allowing bones to withstand stress. The thickness of compact bone remains relatively constant during growth because it is balanced by the processes of bone formation and resorption, ensuring structural integrity.

Wolff's Law

Wolff's Law states that bone adapts to the loads under which it is placed. When mechanical stress is applied to a bone, it remodels itself to become stronger in response. This principle explains why the diameter of long bones increases while maintaining a consistent thickness of compact bone, as the bone adapts to support increased weight and activity.