Musculoskeletal System Overview

Musculoskeletal System

• Bones, muscles, and joints cooperate to form the musculoskeletal system, facilitating movement and support.

Types of Bone

• Long bones: Characterized by a long shaft (diaphysis) and articular surfaces (e.g., tibia, femur).
• Short bones: Cube-shaped (e.g., wrist and ankle bones).
• Flat bones: Thin and often curved (e.g., skull bones such as occipital and parietal bones).
• Irregular bones: Have complex shapes (e.g., vertebrae).
• Sesamoid bones: Embedded within tendons (e.g., patella).

Functions of Bone

• Serve to protect vital organs, provide shape, enable movement, produce blood, store minerals, and contribute to sound production.

Bone Development

• Begins prenatally and completes by around 25 years of age, involving two main processes:
  • Intramembranous ossification
  • Endochondral ossification

Bone Composition

• Consists of 40-50% organic materials, 20% inorganic materials, and 30-40% water.
• Key components include osteocytes, collagen fibers, and an extracellular matrix rich in calcium and phosphate, contributing to strength and rigidity.

Bone Structure

• Cells Present:
  • Osteoblasts: Bone-forming cells, single nucleus, become trapped in lacunae during development.
  • Osteocytes: Mature bone cells derived from osteoblasts, have multiple extensions.
  • Osteoclasts: Multinucleated cells responsible for bone resorption, important for maintaining bone shape.

Bone Tissue

• Compact bone: Dense, with numerous Haversian systems, constituting about 80% of the skeleton; provides strength and support.
• Cancellous (spongy) bone: Lighter, composed of a lattice of trabeculae; contains red bone marrow and lacks Haversian systems.

Periosteum

• A vascular fibrous membrane covering the bone surface, essential for nourishment, muscle attachment, and assisting in bone formation and repair.

Bone Healing Stages

• Formation of fibrocartilaginous callus post-injury, followed by resorption of dead bone and development of spongy bone.
• Callus size inversely related to movement; less movement leads to smaller callus.
• Spongy bone gradually replaced by lamellar bone; final remodeling takes years.

Factors Influencing Healing

• Delays can arise from infection, blood supply deficiencies, age, certain medications, and tissue fragments.
• Promoters of healing include limited movement, nutrition, age, and pain management.

Common Bone Conditions

• Acromegaly: Excessive bone growth in face, hands, and feet.
• Fibrous dysplasia: Abnormal bone growth or swelling.
• Rickets: Vitamin D deficiency leading to impaired bone development in children.
• Osteoporosis: Decreased bone density and strength.
• Osteomyelitis: Infection of bones, often chronic and linked to microbes like Staphylococcus aureus.
• Bone cancer: Primarily osteosarcomas and chondrosarcomas, with many instances stemming from cancers in other organs.

Conclusion

• Understanding the composition, development, structure, function, and diseases of bones is crucial for recognizing their role in overall human biology and health.