Cartilage and Bone Quiz

Cartilage

• Cartilage is a tough, durable connective tissue
• Characterized by an extracellular matrix (ECM) with high concentrations of glycosaminoglycans and proteoglycans
• These interact with collagen and elastic fibers
• Firm consistency allows it to bear mechanical stresses without permanent distortion
• Provides cushioning and sliding regions within skeletal joints
• Guides development and growth of long bones, pre- and post-birth

Chondrocytes

• Cartilage consists of cells called chondrocytes embedded in the ECM
• Chondrocytes synthesize and maintain all ECM components
• Located in matrix cavities called lacunae
• Young chondrocytes are called chondroblasts

Blood Supply

• All types of cartilage lack vascular supplies
• Chondrocytes receive nutrients by diffusion from capillaries in the surrounding connective tissue (perichondrium)
• Cartilage lacks nerves

Perichondrium

• Sheath of dense connective tissue surrounding cartilage in most locations
• Forms an interface between cartilage and supported tissues
• Shelters the blood supply serving the cartilage
• Contains a small neural component

Articular Cartilage

• Covers the ends of bones in movable joints
• Erodes in the course of arthritic degeneration
• Lacks perichondrium and relies on diffusion of oxygen and nutrients from the synovial fluid

Three Main Types of Cartilage

• Hyaline Cartilage:
  • Homogenous and semitransparent
  • Located in articular surfaces of movable joints, walls of respiratory passages (nose, larynx, trachea, bronchi), ventral ends of ribs, and epiphyseal plates of long bones
  • Provides smooth, low-friction surfaces in joints and structural support for the respiratory tract
• Elastic Cartilage:
  • Similar to hyaline cartilage but with abundant elastic fibers
  • Found in the auricle of the ear, external auditory canal, epiglottis, and upper respiratory tract
  • More flexible than hyaline cartilage
• Fibrocartilage:
  • Interaction of hyaline cartilage and dense connective tissue
  • Found in intervertebral discs, attachments of certain ligaments, and the pubic symphysis
  • Very tough, yet cushioning support tissue for bone
  • Lacks a distinct perichondrium

Bone Tissue

• Specialized connective tissue composed of calcified extracellular bone matrix
• Main function: provides mechanical and metabolic support to the body
• Protections of vital organs such as cranial and thoracic cavities
• Encloses internal (medullary) cavities containing bone marrow (where blood cells are produced)
• Reservoir of calcium, phosphate, and other ions
• Participates in skeletal muscle contraction and bodily movements
• Provides solid support for the body

Components of Bone

• Canaliculi: Thin cylindrical spaces facilitating exchanges between osteocytes and blood capillaries
• Endosteum: Layers of connective tissue with osteogenic cells lining the internal surface of bones
• Periosteum: Similar layer of tissue with osteogenic cells covering the external surface of bones

Bone Cells

• Osteoblasts:
  • Derived from mesenchymal stem cells
  • Produce organic components of bone matrix (Type 1 collagen, proteoglycans, osteonectin)
  • Deposit inorganic components, including hydroxyapatite
  • Differentiate into osteocytes
  • Form a single layer of cuboidal cells
• Osteocytes:
  • Most abundant cells in bone
  • Detect mechanical load and stress/fatigue-induced microdamage
• Osteoclasts:
  • Large, multinucleated, motile cells
  • Essential for matrix resorption during bone growth and remodeling
  • Derived from bone marrow-derived monocytes
  • Resorption lacunae are known as Howship's lacunae

Bone Matrix

• Inorganic: ~50% of dry bone weight, mainly hydroxyapatite, bicarbonate, magnesium, potassium, and sodium ions. Non-crystalline calcium phosphate
• Organic: ~90% Type I collagen, small proteoglycans, osteonectin, and osteocalcin. Phosphatases promote calcification.

Compact vs Cancellous Bone

• Compact Bone (Cortical Bone):
  • Dense, outer layer of bones
  • 80% of total bone mass
• Cancellous Bone (Trabecular Bone/Spongy Bone):
  • Deeper structures with numerous interconnecting cavities
  • 20% of total bone mass

Woven vs Lamellar Bone

• Woven Bone:
  • Immature bone, primary bone, bundle bone
  • Newly calcified; irregular and random arrangement of cells and collagen
• Lamellar Bone:
  • Mature bone, secondary bone
  • Remodeled from woven bone; all normal regions of adult bone; parallel bundles of collagen in thin layers (lamellae)

Osteogenesis

• Intramembranous Ossification: Osteoblasts differentiate directly from mesenchymal tissue and secrete osteoid
• Endochondral Ossification: Pre-existing hyaline cartilage matrix is eroded and invaded by osteoblasts, which begin producing osteoid

Osteon (Haversian System)

• Complex of concentric lamellae surrounding a central canal containing blood vessels, nerves and endosteum
• Constitutes most of compact bone

Epiphyseal Growth Plate

• Also called epiphyseal cartilage
• Responsible for longitudinal bone growth
• Disappears at adult bone development
• Obvious in pediatric patients

Epiphyseal Plates (5 Zones)

• Zone of Reserve Cartilage: Normal or typical hyaline cartilage
• Zone of Proliferation: Cartilage cells divide repeatedly and secrete more Type II collagen and proteoglycans
• Zone of Hypertrophy: Cells are hypertrophic, matrix is condensed, and chondrocytes are terminally differentiated, compressed into spicules, and stiffened by Type X collagen secretion
• Zone of Calcified Cartilage: Chondrocytes undergo apoptosis, releasing matrix vesicles and osteocalcin to begin matrix calcification
• Zone of Ossification: Vessels and osteoprogenitor cells infiltrate, osteoblasts settle, secrete osteoid which becomes woven bone, and remodeled into lamellar bone

Joints

• Junctions between bones, allowing (at least potentially) for bending or movement
• Synarthroses: Very limited to no movement (e.g., intervertebral discs).
• Amphiarthroses: Limited movement (e.g., some ligaments).
• Diarthroses (Synovial Joints): Freely mobile; with a joint cavity filled with synovial fluid and a capsule. Have hyaline articular cartilage. Synovial membrane lines capsule, extend into cavity.

Test your knowledge on the types and functions of cartilage and bone. This quiz covers key topics such as the properties of hyaline and elastic cartilage, the role of the extracellular matrix, and the functions of bone structures. Perfect for students in anatomy or physiology courses.