Bone & Bone Tissue

Key Terms in Bone Anatomy and Function

Bone Functions

  • Shape: Provides form and structure to the body.

  • Support: Provides support for body weight and soft tissues.

  • Protection: Protects vital organs such as the brain, heart, and lungs.

  • Movement: Works in tandem with muscles to produce movement.

  • Electrolyte Lane: Stores and releases essential minerals.

  • Blood Production: Hematopoiesis occurs in red bone marrow.

  • Acid-base Balance: Assists in regulating blood pH levels.

Classification of Bones

Characteristics of Bone Classifications

  • Different bone classifications include: long, short, flat, irregular, and sesamoid bones.

  • Common examples include:

    • Long Bones: Femur, humerus

    • Short Bones: Carpals, tarsals

    • Flat Bones: Skull, sternum

    • Irregular Bones: Vertebrae, pelvis

    • Sesamoid Bones: Patella

Parts of Long Bone

  1. Epiphysis: End part of a long bone that is often enlarged to facilitate joint movement.

  2. Diaphysis: The shaft of the long bone.

  3. Medullary Cavity: Hollow part of the bone containing bone marrow.

  4. Endosteum: Inner lining of the bone, involved in bone growth and repair.

  5. Epiphyseal Plate: Growth plate found in long bones.

  6. Epiphyseal Line: Remnant of the epiphyseal plate after bone growth has completed.

Bone Tissue (Osseous Tissue)

Bone Cells

  • Osteoblasts: Bone-forming cells responsible for producing new bone.

  • Osteocytes: Mature bone cells that maintain bone tissue.

  • Osteoclasts: Bone-resorbing cells that break down bone tissue.

Characteristics of Bone

  • Bone is a hard, strong, and living tissue.

Factors Affecting Bone Growth

  • Nutrition

  • Hormones

  • Physical activity

  • Age

Types of Bone Tissue

  1. Compact Bone

    • Characteristics: Dense and strong, forms the outer layer of bones.

    • Components:

      • Canaliculi: Microscopic canals that connect osteocytes and allow nutrient exchange.

      • Lacunae: Small spaces housing osteocytes.

      • Lamellae: Concentric rings of bone matrix that form the structural unit.

      • Haversian (Osteonic) Canals: Central canals that contain blood vessels and nerves.

      • Volkmann's Canals: Transverse passageways that connect Haversian canals.

      • Osteon: The basic structural unit of compact bone.

  2. Spongy Bone (Cancellous Bone)

    • Characteristics: Lightweight and porous, reducing bone weight while maintaining strength.

    • Components:

      • Trabeculae: Thin plates of bone forming a lattice framework that supports stress.

  3. Bone Marrow

    • Red Bone Marrow: Responsible for blood cell production (hematopoiesis).

    • Yellow Bone Marrow: Stores fat.

Bone Remodeling

Key Terms

  • Resorption: The process by which osteoclasts break down bone tissue.

  • Ossification: The process of bone formation carried out by osteoblasts.

  • Remodeling: The continuous process of bone breakdown and rebuilding.

Bone Diseases

  • Osteoporosis: A condition characterized by decreased bone density and an increased risk of fractures.

    • Risk Factors for Osteoporosis: Aging, menopause, lack of vitamin D or calcium, smoking.

  • Osteopenia: A condition where bone density is lower than normal, but not low enough to be classified as osteoporosis.

Types of Fractures

  1. Simple Fracture: The bone remains aligned and surrounding tissue is intact.

  2. Compound Fracture: The bone pierces through the skin.

  3. Greenstick Fracture: An incomplete fracture that does not completely break the bone.

  4. Comminuted Fracture: The bone breaks into multiple fragments.

  5. Spiral Fracture: A fracture caused by a twisting force.

Fracture Repair

  1. Factors Impacting Fracture Repair:

    • Complexity of fracture

    • Poor blood supply

    • Age

    • Poor nutritional status

  2. Steps in the Fracture Repair Process:

    • Step 1: Hematoma formation at the fracture site.

    • Step 2: Fibrocartilaginous callus formation occurs, laying down a temporary bridge.

    • Step 3: Bony callus formation, where the fibrocartilage is replaced with bony tissue.

    • Step 4: The bone is reshaped into its original structure, restoring its integrity.