BONE PHYSIOLOGY

• Main components of the Skeletal System:

  • Bone
  • Cartilage
  • Ligaments (hold bones together)
  • Tendons (connect muscles to bones)
  • Adult bones: average of 206 bones
  • Skeletal system serves as a framework of the body and has other functions
• Three types of cartilage: hyaline cartilage, fibrocartilage, and elastic cartilage

  • Most bones start out as a hyaline cartilage model
  • Most cartilage is covered by a protective connective tissue sheath called the perichondrium
• Hyaline Cartilage Growth:

  • New cartilage is added to the surface by chondroblasts from the inner layer of the perichondrium
  • New cartilage is formed within the cartilage by chondrocytes that divide and produce additional matrix
• Bone Histology:

  • Bone Matrix composed of a mixture of organic (35%) and inorganic materials (65%) for bone strength
  • Bone cells derived from mesenchymal cells:
  • Osteoblasts (bone-forming cells)
  • Osteocytes (mature bone cells)
  • Osteoclasts (bone resorption)
• Two types of Ossification:

  • Intramembranous Ossification:
  • Starts with a membrane within a mesenchymal skeleton
  • Endochondral Ossification:
  • Mesenchymal skeleton -> cartilage -> bone
• Bone Growth:

  • Bone Length:
  • Located at the epiphyseal plate
  • Organized into 5 zones
  • Bone Width:
  • Appositional growth at the bone surface
  • Articular Cartilage:
  • Increases epiphysis
  • Similar zones but do not ossify
  • Factors affecting bone growth: Nutrition (Vit. C and D), Hormones (Growth, Thyroid, Reproductive)
• Bone Repair Mechanism
• Calcium Homeostasis:

  • Role of Calcium in muscle contraction and cellular exocytosis
  • Regulated by three hormones: Parathyroid hormone (PTH), Calcitriol, Calcitonin
• Selected Skeletal Disorders:

  • Dwarfism
  • Gigantism
  • Osteomyelitis (bacterial infection of the bone)
  • Osteomalacia (softening of adult bones due to calcium depletion)
  • Rickets (growth retardation due to nutritional deficiencies in minerals or vitamin D)
• Main components of the skeletal system:

  • Bone
  • Cartilage
  • Ligaments (hold bones together)
  • Tendons (connect muscles to bones)
• Adult human body has an average of 206 bones
• Skeletal system serves as the framework of the body and has other functions
• Three types of cartilage:

  • Hyaline cartilage
  • Fibrocartilage
  • Elastic cartilage
• Hyaline Cartilage growth:

  • Appositional growth: new cartilage added to the surface by chondroblasts
  • Interstitial growth: new cartilage formed within by chondrocytes
• Bone Matrix:

  • Composed of organic (35%) and inorganic materials (65%) providing bone strength
• Bone cells derived from mesenchymal cells:

  • Osteoblasts (bone-forming cells)
  • Osteocytes (mature bone cells)
  • Osteoclasts (bone resorption)
• Types of bones based on the amount of matrix:

  • Spongy Bone: porous with less matrix and more spaces
  • Compact bone: solid outer layer with more matrix and denser structure
• Bone development:

  • Intramembranous Ossification: starts with a membrane within a mesenchymal skeleton
  • Endochondral Ossification: mesenchymal skeleton transforms into cartilage then bone
• Bone Growth:

  • Bone Length: occurs at the epiphyseal plate with zones of resting cartilage, proliferation, hypertrophy, ossification, and ossified bone
  • Bone Width: appositional growth at the bone surface
  • Articular Cartilage: increases epiphysis, does not ossify, and persists through life
• Factors affecting bone growth:

  • Nutrition
  • Vitamins C and D
  • Hormones: Growth, Thyroid, and Reproductive Hormones
• Bone Repair process:

  • Hematoma formation
  • Callus formation
  • Callus ossification
  • Bone remodeling
• Calcium Homeostasis:

  • Regulated by Parathyroid hormone (PTH), Calcitriol, and Calcitonin
  • Functions in muscle contraction and cellular exocytosis
• Selected Skeletal Disorders:

  • Dwarfism: small body size due to improper growth at epiphyseal plates
  • Gigantism: increased body size due to excessive growth at epiphyseal plates
  • Osteomyelitis: bacterial infection of the bone
  • Osteomalacia: softening of adult bones due to calcium depletion
  • Rickets: growth retardation due to nutritional deficiencies in minerals or vitamin D