Cartilaginous Tissue Overview

Study Notes

Specialized connective tissue
Main cells are chondrocytes, occupying small cavities called lacunae in the matrix
Matrix is firm but flexible, resistant to mechanical forces
Matrix composed of GAGs, proteoglycans, type II collagen fibers, and sometimes elastic fibers
Avascular tissue, cells nourished by diffusion through the matrix
Large pieces of cartilage have channels for blood vessels and nerves
Surrounded by perichondrium, a connective tissue sheath
Perichondrium has two layers: outer fibrous (collagen type I, fibroblasts, vascularized) and inner cellular (chondroblasts that secrete matrix)
Chondrocytes are responsible for secreting matrix
Lacunae (small cavities) house chondrocytes
Chondrocytes form groups within the same lacunae, called isogenic groups
Interstitial growth arises from chondrocytes' division and secretion of matrix within the lacunae
Cells grow in different compartments and increase the size and volume of the tissue

During embryonic development, mesenchymal stem cells retract their extensions and group together, forming chondrification centers
Under the influence of stimuli, these cells differentiate into chondroblasts
Chondroblasts secrete matrix, then transform into chondrocytes when surrounded by matrix
Chondrocytes retain their ability to divide
Can form isogenic groups (groups of cells within same lacuna)
When cells secrete matrix, they separate, making the cartilage grow from within (interstitial growth)

Hyaline cartilage: most abundant type, flexible, semi-translucent, bluish-gray color, uniform, resistant to tensile/compression forces
- Precursor to long bones in embryonic development
- Found in nasal cartilages, larynx, trachea/bronchi, ribs, and articular surfaces
Elastic cartilage: similar to hyaline, but contains abundant elastic fibers, very flexible, yellowish color, more opaque compared to hyaline
- Found in the external ear, auditory tubes, epiglottis, and parts of the larynx
Fibrocartilage: intermediate between cartilage and dense CT, contains more type I collagen, has scarce matrix, less water and proteoglycans, and great tensile strength
- Has chondrocytes aligned in parallel rows
- Found in intervertebral discs, tendons/ligaments, and the pubic symphysis

Interstitial growth: chondrocytes divide within cartilage and secrete new matrix, expanding cartilage from within
Apositional growth: new chondrocytes are formed from the perichondrium, an outer connective tissue layer
- It adds cartilage layers to the outside, increasing cartilage thickness