Lecture Notes: Bone Anatomy and Physiology

Introduction

• Bone as an organ: Living cells and tissues.
• Tissue types in bone: Epithelial, connective, nervous, muscle.
• Osseous tissue: Bone is primarily a connective tissue.

Composition and Structure

• Organic components:
  • Made by cells (osteoid).
  • Includes collagen and ground substance.
• Inorganic components:
  • Derived from diet, includes calcium.
  • Calcium phosphate and calcium hydroxide form hydroxyapatite.

Bone Functions

• Support and protection: Framework for the body and protection for organs.
• Movement: Muscles attach to bones, acting as levers.
• Hemopoiesis: Blood cell production in spongy bone (red bone marrow).
• Storage: Energy storage (fat), minerals (calcium).

Classification of Bones

• Long bones: Longer than they are wide (e.g., humerus, femur).
• Short bones: Roughly equal in length and width (e.g., carpals).
• Flat bones: Thin and provide protection (e.g., cranial bones).
• Irregular bones: Complex shapes (e.g., vertebrae).

Anatomy of Long Bones

• Diaphysis (shaft): Contains compact bone and medullary cavity.
• Epiphyses: Ends of long bones, site of secondary ossification.
• Metaphysis: Contains the epiphyseal growth plate.
• Articular cartilage: At the ends for smooth movement.
• Periosteum: Outer layer of bone, dense irregular connective tissue.
• Endosteum: Lines the medullary cavity, contains bone cells.

Bone Cells

• Osteoprogenitor cells: Stem cells for bone.
• Osteoblasts: Produce osteoid, involved in bone formation.
• Osteocytes: Maintain bone matrix, communicate via canaliculi.
• Osteoclasts: Break down bone, key in remodeling and calcium release.

Bone Formation (Ossification)

• Intramembranous ossification:
  • Forms flat bones like cranial bones.
  • Osteoblasts lay down osteoid in mesenchyme.
• Endochondral ossification:
  • Forms most bones, including long bones.
  • Begins with a hyaline cartilage model.

Bone Growth and Remodeling

• Growth plates: Sites of bone growth during development.
• Remodeling: Ongoing replacement of old bone.
  • Balances resorption and formation.
  • Influenced by mechanical stress and hormonal changes.

Factors Affecting Bone Health

• Exercise: Increases bone density through mechanical stress.
• Age: Reduces efficiency in bone formation, leads to osteoporosis.

Bone Repair Process

• Hematoma formation: Blood clot forms as initial response.
• Soft callus formation: Fibrocartilaginous tissue forms.
• Hard callus formation: Woven bone replaces soft callus.
• Bone remodeling: Converts woven bone to lamellar bone over time.

Conclusion

• Understanding bone dynamics is crucial for studying human physiology and pathology.
• Next focus: Articulations.