Hyaline, elastic and fibrocartilage, differing in fibre content
Mnemonic
Three types, distinguished by which fibre dominates:
- Hyaline - type II collagen, fine fibres, glassy. The commonest. Articular surfaces, costal cartilage, trachea and bronchi, the fetal skeleton, growth plates
- Elastic - type II collagen plus elastic fibres. Ear, epiglottis, external auditory meatus, Eustachian tube
- Fibrocartilage - type I collagen, coarse bundles. Intervertebral discs, menisci, pubic symphysis, tendon insertions. Has no perichondrium
“Hyaline for joints, elastic for the ear, fibrocartilage for the discs.”
All cartilage is avascular and aneural, nourished by diffusion, which is why it heals so poorly and why articular cartilage damage tends to be permanent.
Fibrocartilage is the tough one, built to resist compression and shear, which is why it sits wherever two bones grind together and why it is what a torn meniscus is made of.
Expansion
| Type | Matrix | Sites |
|---|---|---|
| Hyaline | Type II collagen, glassy | Articular surfaces, costal cartilage, trachea and bronchi, nasal septum, epiphyseal plate, fetal skeleton |
| Elastic | Type II plus elastic fibres | External ear, epiglottis, auditory tube |
| Fibrocartilage | Type I collagen, dense | Intervertebral disc, menisci, pubic symphysis, tendon insertions |
Common properties: all cartilage is avascular, aneural and alymphatic, nourished by diffusion from the perichondrium or synovial fluid. Chondrocytes sit in lacunae, often in isogenous groups.
Fibrocartilage is the exception in having no perichondrium, which together with avascularity explains the poor healing of meniscal and disc injuries, and the reliance on fibrocartilaginous scar when articular cartilage is damaged.
Growth occurs two ways: interstitial (from within, at the epiphyseal plate) and appositional (from the perichondrium).
Cartilage calcifies with age, which is why costal cartilages become visible radiographically and why the larynx ossifies.