Question 1

What are the main components of the bone matrix?

Accepted Answer

The bone matrix consists of organic and inorganic components. About two-thirds comprises inorganic salts, primarily calcium phosphate combined with calcium hydroxide to form hydroxyapatite crystals. One-third is organic osteoid, mainly composed of collagen fibers and glycoproteins like proteoglycans. Together, these components create bone's unique hardness and strength.

Question 2

How does collagen contribute to bone strength?

Accepted Answer

Collagen provides structure and elasticity to bone tissue, preventing it from becoming brittle and shattering easily. The triple-helical collagen fibrils form the framework where hydroxyapatite crystals mineralize, creating mineralized fibers arranged in parallel lamellae. Without collagen, bones would lack the flexibility needed to withstand tensile forces.

Question 3

What role do proteoglycans play in bone matrix function?

Accepted Answer

Proteoglycans are glycoproteins in the organic osteoid component that absorb and retain water within the bone matrix. This water retention makes bones resistant to compression forces, contributing to their ability to support body weight and withstand mechanical stress. Proteoglycans work alongside collagen to provide the matrix's mechanical resilience.

Question 4

How do hydroxyapatite crystals form in bone?

Accepted Answer

Hydroxyapatite crystals form when calcium phosphate combines with calcium hydroxide in microscopic spaces between collagen fibers. As crystallization occurs, the crystals incorporate additional inorganic salts including magnesium hydroxide, fluoride, and sulfate. These mineralized crystals deposited on collagen fibers confer hardness and rigidity to bone tissue.

Question 5

Why does bone remain flexible despite being hard?

Accepted Answer

Bone's flexibility comes from its dual composition: collagen provides elasticity and tensile strength, while hydroxyapatite crystals provide hardness and compressive strength. This combination allows bone to withstand both compressive and tensile forces without becoming brittle. An acid dissolution experiment demonstrates this—removing minerals leaves a flexible, rubbery bone.

Question 6

How does the bone matrix function as a mineral reservoir?

Accepted Answer

The bone matrix acts as a reservoir for physiologically important minerals, especially calcium and phosphorus. When the body requires these minerals, osteoclasts secrete enzymes and acids to break down the matrix and release minerals into the bloodstream. This maintains optimal calcium and phosphorus levels essential for muscle contractions and nerve impulse transmission.

Question 7

What percentage of bone mass is contributed by cells versus matrix?

Accepted Answer

Bone is primarily composed of matrix components, with only 2 to 3 percent of bone mass contributed by cells. The remaining 97 to 98 percent consists of the bone matrix—both organic osteoid and inorganic mineral salts. This composition makes bone a supportive connective tissue with exceptional structural properties.

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