Lecture Notes on Bone Structure and Function

Introduction to Bones

• Bones are a type of connective tissue.
• Skeleton composed of bones and skeletal cartilage.

Skeletal Cartilage

• Contains water: Allows tension and compression resistance.
• Chondrocytes: Cells inside lacunae, part of the extracellular matrix.
• Types of Cartilage:
  • Hyalin: Found in nose, ribs, larynx, bone ends.
  • Elastic: Found in ears, epiglottis.
  • Fibrocartilage: Found between vertebrae.

Types of Bones

• Axial: Skull, spine, ribcage.
• Appendicular: Limbs (arms, legs), pelvis, shoulders.
• Shapes:
  • Long: E.g., limb bones.
  • Short: Cube-like, found in ankles, wrists.
  • Flat: Thin, curved, e.g., sternum.
  • Irregular: Complex shapes, e.g., vertebrae.

Functions of Bones

• Support: Structural framework for the body.
• Protection: E.g., ribcage protects the heart.
• Movement: Operate as levers.
• Mineral Storage: Calcium and phosphate.
• Other Functions: Fat storage, hormone production, blood cell formation.

Bone Structure

• Bone vs. Organ: Bone is a tissue; actual bones are organs with multiple tissue types.
• Tissue Types: Bone tissue, nervous, connective, cartilage, blood vessels.

Gross Anatomy of Bones

• Compact Bone: Dense outer layer.
• Spongy Bone: Honeycomb structure, filled with marrow.
• Bone Types:
  • Long bones: Diaphysis (shaft), epiphyses (ends), contain marrow.
  • Short, irregular, flat bones: Thin plates of spongy bone.
• Bone Coverings:
  • Periosteum: Outer fibrous and inner osteogenic layer.
  • Endosteum: Covers internal surfaces.
• Bone Markings: Projections, depressions, and openings.

Microscopic Anatomy of Bones

• Bone Cells:
  • Osteogenic Cells: Stem cells dividing in periosteum/endosteum.
  • Osteoblasts: Secrete bone matrix, active in growth.
  • Osteocytes: Mature cells maintaining bone matrix.
  • Bone Lining Cells: Maintain bone surface.
  • Osteoclasts: Break down bone for resorption.
• Compact Bone Structure:
  • Osteons: Cylindrical units with central canals.
  • Lamellae: Hollow tubes arranged like tree rings.
  • Central Canal: Contains blood vessels and nerves.
  • Canaliculi: Connect lacunae, supporting cell communication.
• Bone Composition:
  • Organic Components: Cells, osteoid (ground substance and collagen).
  • Inorganic Components: Hydroxyapatites (calcium phosphate crystals).

Conclusion

• Understanding bone structure is crucial for comprehending the human skeleton's formation and function.