Anatomy_and_Physiology_of_Bones

Page 2: Anatomy and Physiology of Bones

  • Skeletal System:

    • Comprises bones and cartilage.

    • Ligaments connect bones to form a structural framework for body tissues.

Page 3: Functions of the Skeletal System

  • Support and Movement:

    • Bones attach to ligaments and tendons, creating a framework for movement.

    • Movement is achieved through the cooperation of levers, muscles, tendons, and ligaments.

  • Protection:

    • Bones safeguard vital organs:

      • Cranium around the brain.

      • Vertebral column protects spinal cord.

      • Ribcage surrounds heart and lungs.

      • Pelvis protects urogenital organs.

  • Mineral Homeostasis:

    • Bones store minerals:

      • 99% of the body’s calcium.

      • 85% of phosphate.

      • 50% of magnesium.

  • Blood-Cell Formation:

    • Blood cells arise from haemopoietic stem cells in red bone marrow.

    • Infants have red marrow which transitions to yellow marrow over time due to reduced erythropoietin.

Page 4: Bone Composition and Structure

  • Bone Matrix Components:

    • 25% organic matrix (osteoid).

    • 50% inorganic minerals (mineral salts).

    • 25% water.

  • Bone Tissue Types:

    • Cortical Bone: Compact bone.

    • Cancellous Bone: Spongy bone.

  • Cortical Bone Elements:

    • Periosteum.

    • Intracortical area.

    • Endosteum.

Page 5: Bone Structure and Blood Supply

  • Osteon Structure:

    • Osteons (Haversian systems) are cylindrical structures with concentric layers (lamellae).

    • Osteocytes reside in lacunae among the lamellae.

    • Central (Haversian) canal contains blood vessels, lymph vessels, and nerves.

  • Blood Supply:

    • Bone and marrow are highly vascularized (10-20% of cardiac output).

    • Blood sources include nutrient artery, periosteal, epiphyseal, and metaphyseal arteries.

Page 6: Bone Growth and Development

  • Embryonic Development:

    • Bones develop in first eight weeks of gestation; initial skeleton is connective tissue.

  • Ossification:

    • Connective tissue structures undergo intramembranous or endochondral ossification (cartilage to bone).

  • Growth Plates:

    • Epiphyseal growth plate consists of zones: resting, growth, hypertrophic, calcification.

  • Skeletal Maturity:

    • 90% of adult bone formation by the end of adolescence; full maturity at 20-25 years.

Page 7: Factors Affecting Bone Health

  • Calcium:

    • Vital for bone mineralization; deficiency linked to osteoporosis and osteomalacia.

  • Vitamins:

    • Vitamin D: Enhances calcium absorption.

    • Vitamin A: Necessary for osteoblasts; Vitamin C: Important for collagen synthesis.

  • Exercise:

    • Weight-bearing exercise crucial for bone density and strength.

  • Aging:

    • Aging leads to decreased strength and elasticity, increasing fracture risk due to mineral loss and collagen flexibility reduction.

Page 8: Types of Bones

  • Long Bones:

    • Longer than wide (e.g., humerus, radius, tibia, femur); consist of diaphysis (shaft) and epiphyses (ends).

  • Short Bones:

    • Cube-shaped, mainly cancellous bone with outer cortical layer (e.g., wrist and ankle bones).

  • Flat Bones:

    • Thin and slightly curved; contain cancellous bone between cortical layers (e.g., skull, ribs, scapula).

  • Irregular Bones:

    • Do not fit specific categories, composed of cancellous and cortical bone (e.g., vertebrae, pelvis).

  • Sesamoid Bones:

    • Round or oval, develop within tendons (e.g., patella).