Which fibers provide tensile strength to bone due to being organized at 45 degree angles from each other?

• A. Collagen
• B. Elastin
• C. Reticulin
• D. Fibrin

Answer: (A)

Tensile strength in bone mainly comes from collagen type I fibers arranged in laminated layers. These fibers run at about 45 degrees to the long axis within each lamella, and neighboring lamellae orient in different directions (often rotating by ~90 degrees). This alternating, angled organization creates a twisted plywood pattern that resists pulling and twisting from multiple directions, giving bone toughness and resistance to fracture. The other fibers listed don’t provide this structural tensile framework in bone: elastin adds elasticity in soft tissues, reticulin forms delicate networks in organs, and fibrin is involved in blood clotting. So collagen is the fiber responsible for that directional tensile strength.