Skeletal System and Bone Tissue

Overview of the Skeletal System

  • The skeletal system provides structure and support to the body, protects organs, facilitates movement, stores minerals, and produces blood cells.

Structure of Bone

  • Parts of a Long Bone:

    • Proximal epiphysis: End part of the bone closest to the body.

    • Distal epiphysis: End part furthest from the body.

    • Diaphysis: Shaft or central part of the bone.

    • Metaphysis: Area where diaphysis meets epiphysis, contains growth plate in growing bones.

    • Articular cartilage: Smooth tissue at the ends of bones to reduce friction in joints.

    • Periosteum: Protective outer layer of bone with blood vessels and nerves.

    • Compact bone: Dense, hard tissue that forms the outer layer of bone.

    • Spongy bone: Lattice-like bone tissue that contains red bone marrow.

    • Medullary cavity: Central cavity of bone that contains yellow or red bone marrow.

    • Epiphyseal line: Mark separating the epiphysis from the diaphysis in mature bones.

Bone Tissue Composition

  • Types of Bone Tissue:

    • Compact Bone: Contains osteons, which are the structural units, made of concentric lamellae.

    • Spongy Bone: Contains trabeculae (small beam-like structures) and accommodates bone marrow.

  • Cells in Bone Tissue:

    • Osteoblasts: Cells that form new bone.

    • Osteocytes: Mature bone cells that maintain the bone matrix.

    • Osteoclasts: Cells that break down bone tissue.

Bone Development Process

  1. Development of Ossification Centre:

    • Osteoblasts start to secrete organic extracellular matrix.

  2. Calcification:

    • Calcium and other minerals are deposited, hardening the extracellular matrix.

  3. Formation of Trabeculae:

    • The extracellular matrix develops into trabecular structures, leading to spongy bone formation.

  4. Development of the Periosteum:

    • Mesenchyme (embryonic connective tissue) develops into the periosteum around the bone.

Cartilage Model Development

  1. Development of Cartilage Model:

    • Mesenchymal cells differentiate into chondroblasts to form a cartilage model.

  2. Growth of Cartilage Model:

    • Growth occurs through chondrocyte cell division.

  3. Formation of Medullary Cavity:

    • Osteoclast-mediated bone breakdown forms the medullary (marrow) cavity.

  4. Development of Secondary Ossification Centres:

    • These form in the epiphyses after the primary ossification.

  5. Formation of Articular Cartilage and Epiphyseal Plate:

    • These structures remain as hyaline cartilage.

Bone Healing Process

  1. Formation of Fracture Hematoma:

    • Blood vessels rupture and bleeding occurs, forming a hematoma at the fracture site.

  2. Fibrocartilaginous Callus Formation:

    • Fibroblasts and chondroblasts create a soft tissue bridge across the fracture.

  3. Bony Callus Formation:

    • Osteoblasts convert the fibrocartilaginous callus to a bony callus made of spongy bone.

  4. Bone Remodeling:

    • Osteoclasts trim excess material, and compact bone is remodeled around the fracture site.

Types of Bone Fractures

  • Open/Compound Fracture: Bone breaks through the skin.

  • Comminuted Fracture: Bone shatters into multiple pieces.

  • Greenstick Fracture: Incomplete fracture, often seen in children (bone bends).

  • Impacted Fracture: Bone fragments are driven into each other.

  • Pott's Fracture: Fracture of the distal fibula.

  • Colles Fracture: Fracture of the distal radius.

Conclusion

  • Understanding the structure, development, and healing of bone is critical for paramedic science and overall health.