Cartilage Tissue Quiz

Cartilage

• Cartilage is a tough, durable connective tissue.
• It's characterized by an extracellular matrix (ECM) with a high concentration of glycosaminoglycans and proteoglycans.
• These interact with collagen and elastic fibers.
• The ECM provides a firm consistency that allows cartilage to withstand mechanical stress without permanent distortion.
• Cartilage acts as a cushion and facilitates smooth movement within skeletal joints.
• Cartilage guides the development and growth of long bones.

Chondrocytes

• Cartilage consists of cells called chondrocytes, embedded in the ECM.
• Chondrocytes synthesize and maintain all ECM components.
• They are located in cavities within the matrix called lacunae.
• Young chondrocytes are called chondroblasts.

Blood Supply of Cartilage

• All types of cartilage lack vascular supplies.
• Chondrocytes receive nutrients via diffusion from capillaries in the surrounding connective tissue, called the perichondrium.
• Cartilage lacks nerves.

Perichondrium

• Perichondrium is a sheath of dense connective tissue that surrounds most cartilage.
• It forms an interface between the cartilage and the tissues it supports.
• The perichondrium provides blood supply to the cartilage.
• It also encapsulates cartilage and a small neural component, supporting the cartilage's functioning.
• Articular cartilage lacks perichondrium.
• It's nourished by the diffusion of oxygen and nutrients from the synovial fluid.

Three Main Types of Cartilage

• Hyaline cartilage
• Elastic cartilage
• Fibrocartilage

Hyaline Cartilage

• Most common type of cartilage.
• Homogenous and semitransparent in its fresh state.
• Located in articular surfaces of movable joints, walls of major respiratory passages (nose, larynx, trachea, bronchi), ventral ends of ribs where they articulate with the sternum, and epiphyseal plates of long bones.
• Plays a role in longitudinal bone growth.
• In embryos, it forms the initial skeleton that is gradually replaced by bone.
• Hyaline cartilage cells metabolize glucose mainly by anaerobic glycolysis.

Elastic Cartilage

• Similar to hyaline cartilage but with abundant elastic fibers.
• Located in the auricle of the ear, walls of the external auditory canal, epiglottis, and upper respiratory tract.
• More flexible than hyaline cartilage.

Fibrocartilage

• A structure resulting from the interaction of hyaline cartilage and dense connective tissue.
• Found in intervertebral discs, attachments of ligaments, and the pubic symphysis.
• Supports bone and provides cushioning.
• No perichondrium.

Bone Tissue

• Specialized connective tissue with calcified extracellular bone matrix.
• Main function is providing mechanical support and performing metabolic functions.
• Protects vital organs (e.g., cranial and thoracic cavities).
• Encloses internal cavities containing bone marrow where blood cells are produced.
• Serves as a reservoir for calcium, phosphate, and other ions.
• Involved in skeletal muscle contraction and bodily movements.

Components of Bone

• Canaliculi: A thin cylindrical space for exchanges between osteocytes and blood capillaries.
• Endosteum: Layer of connective tissue with osteogenic cells lining the inner surface of the bone.
• Periosteum: Layer of connective tissue with osteogenic cells lining the outer surface of the bone.

Bone Cells

• Osteoblasts: Derived from mesenchymal stem cells; produce the organic components of bone matrix (Type 1 Collagen, proteoglycans, osteonectin).
• Osteocytes: Most abundant bone cells; detect mechanical load and stress-induced microdamage.
• Osteoclasts: Large, multinucleated cells responsible for bone matrix resorption during bone growth and remodeling. Involved in Howship’s lacunae.

Bone Matrix

• Inorganic Matrix: 50% of bone dry weight; mainly hydroxyapatite, with bicarbonate, magnesium, potassium, sodium ions and non-crystalline calcium phosphate.
• Organic Matrix: 90% Type 1 Collagen with small amounts of proteoglycans, osteonectin, osteocalcin, and binding proteins; these support the calcification process.

Compact vs Cancellous Bone

• Compact bone (cortical bone): Dense outer layer, 80% of bone mass.
• Cancellous bone (trabecular bone): Deeper areas with interconnecting cavities, forming 20% of bone mass.

Woven vs Lamellar Bone

• Woven bone: Immature, primary bone, characterized by a haphazard arrangement of fibers; newly calcified.
• Lamellar bone: Mature, secondary bone; remodeled from woven bone; organized into layers (lamellae). All normal adult bone regions.

Osteogenesis (Bone Formation)

• Intramembranous ossification: Osteoblasts develop directly from mesenchymal con-densed tissue sheets and secrete osteoid.
• Endochondral ossification: Pre-existing hyaline cartilage is replaced by bone.

Osteon or Haversian System

• A complex of concentric lamellae surrounding a central canal with vascular elements, nerves, and endosteum; essential part of compact bone.

Epiphyseal Growth Plate

• Also called epiphyseal cartilage; responsible for bone lengthening in children and adolescents.
• Disappears during adulthood.
• Visible in pediatric radiographs (X-rays).

Epiphyseal Plates (5 Different Zones)

• Zone of reserve cartilage (hyaline cartilage).
• Zone of proliferation (cartilage cells actively divide).
• Zone of hypertrophy (chondrocytes swell, matrix stiffens).
• Zone of calcified cartilage (chondrocytes die, matrix calcifies).
• Zone of ossification (cartilage replaced by bone tissue).

Joints

• Places where bones articulate allowing bending or movement
• Synarthroses: Joints with limited movement (e.g., intervertebral discs)
  • Intervertebral discs: Consists of a thick fibrous outer layer (annulus fibrosus) and an inner gel-like core (nucleus pulposus). These help cushion adjacent vertebrae.
• Diarthroses: Freely movable joints characteristically with synovial joints.
  • Joint cavity: Filled with lubricating synovial fluid
  • Fibrous capsule: Encloses the joint cavity.
  • Hyaline articular cartilage: Covers articulating bone ends for smooth movement.
  • Synovial membrane: Lines the fibrous capsule, producing synovial fluid.

Test your knowledge of cartilage tissue! This quiz covers chondrocytes, nutrient sources, perichondrium function, hyaline, elastic, and fibrocartilage types. Explore cartilage's role in resisting stress and its locations throughout the body.