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Anatomy & Physiology: Bone and Cartilage Structure, Growth, and Disorders

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  • Types of cartilage in the skeleton
    Hyaline cartilage provides support with flexibility; elastic cartilage contains elastic fibers for flexibility; fibrocartilage is highly compressible with tensile strength.
  • Functions of bones
    Support, protection, movement, mineral storage, blood cell formation (hematopoiesis), fat storage, and hormone production (osteocalcin).
  • Classification of bones by location
    Axial skeleton includes skull, vertebral column, rib cage; appendicular skeleton includes limbs and girdles.
  • Classification of bones by shape
    Long bones (longer than wide), short bones (cube-shaped), flat bones (thin and curved), irregular bones (complex shapes).
  • Gross structure of bones
    Compact bone forms dense outer layer; spongy bone (trabeculae) inside; marrow fills spaces; covered by periosteum and lined by endosteum.
  • Bone development processes
    Intramembranous ossification forms flat bones from fibrous membranes; endochondral ossification replaces hyaline cartilage to form most other bones.
  • Cartilage growth types
    Appositional growth: new matrix added at surface by chondroblasts; interstitial growth: chondrocytes divide and expand matrix from within.
  • Bone remodeling
    Continuous process of bone deposition by osteoblasts and resorption by osteoclasts to maintain bone strength and calcium homeostasis.
  • Cells of bone tissue
    Osteoprogenitor cells (stem cells), osteoblasts (bone-forming), osteocytes (mature cells maintaining matrix), bone lining cells, osteoclasts (bone-resorbing).
  • Osteon structure
    The osteon is the structural unit of compact bone, consisting of concentric lamellae around a central canal containing blood vessels and nerves.
  • Function of canaliculi
    Tiny canals connecting osteocytes, allowing nutrient and waste exchange despite the hard bone matrix.
  • Chemical composition of bone
    Organic components (cells and osteoid with collagen) provide tensile strength; inorganic components (hydroxyapatite crystals) provide hardness and resistance to compression.
  • Endochondral ossification steps
    Bone collar formation, cartilage calcification, periosteal bud invasion, diaphysis elongation, secondary ossification centers in epiphyses.
  • Zones of longitudinal bone growth
    Resting zone, proliferation zone (cell division), hypertrophic zone (cell enlargement), calcification zone, ossification zone.
  • Hormonal regulation of bone growth
    Growth hormone stimulates epiphyseal plate activity; thyroid hormones modulate growth; sex hormones (estrogen/testosterone) promote growth and epiphyseal closure.
  • Parathyroid hormone (PTH) role in bone
    Increases blood calcium by stimulating osteoclasts to resorb bone, releasing calcium into the bloodstream.
  • Calcitonin function
    Produced by thyroid parafollicular cells; lowers blood calcium by inhibiting osteoclast activity, but has minimal effect at normal levels.
  • Wolff’s law
    Bone grows or remodels in response to mechanical stress, strengthening areas subjected to greater load.
  • Stages of bone fracture repair
    Hematoma formation, fibrocartilaginous callus formation, bony callus formation, bone remodeling.
  • Osteoporosis characteristics
    Decreased bone mass and density due to excessive resorption; bones become porous, fragile, and prone to fractures.
  • Causes and prevention of osteoporosis
    Caused by decreased sex hormones, poor diet, lack of exercise, smoking, genetics; prevented by calcium/vitamin D intake and weight-bearing exercise.
  • Osteomalacia and rickets
    Softening of bones due to defective mineralization from vitamin D or calcium deficiency; rickets is the childhood form causing bone deformities.
  • Paget’s disease
    Excessive, disorganized bone remodeling causing enlarged but weak bones; often affects spine, pelvis, femur, and skull.