Bone

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Bones are connected to each other to form skeleton, which forms the framework of the body. Bone tissue is formed by collagen matrix hardened by deposited calcium.

Functions

Mechanical

• Protect internal organs
• Give shape and support to the body
• Movement

Synthetic

• Manufactures blood cells from the bone marrow (hematopoiesis)

Metabolic

• Mineral storage
• Fat storage
• Role in acid-base balance

Structure

Individual bone structure

• Compact/cortical bone - makes up outer part of bone, rigid
• Cancellous/spongy bone - makes up inner part of bone, more porous, storage of bone marrow

Cellular structure

• Osteoblasts - produce matrix (osteoid), build up bone tissue
• Osteoclasts - secretes acids and enzymes to breakdown bone tissue
• Osteocytes - maintain bone tissue by mineralising osteoid

Molecular structure

Matrix

• Inorganic
• Organic

Remodeling

Purpose

• To allow bone to ordinarily adjust strength in proportion to the degree of bone stress. When subjected to heavy loads, bones will consequently thicken.
• To rearrange shape of bone for proper support of mechanical forces in accordance with stress patterns.
• To replace old bone which may be brittle/weak in order to maintain toughness of bone. New organic matrix is needed as the old organic matrix degenerates.

Calcium homeostasis/balance must exist between osteoclasts and osteoblasts activity

• If too much new tissue is formed, the bones become abnormally large and thick (acromegaly)
• Excessive loss of calcium weakens the bones, as occurs in osteoporosis

Disorders

• Osteoporosis
• Osteoarthritis
• Osteomalacia
• Rickets
• Epiphyseal plate disorders

References

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