Hyaline cartilage
Cartilago hyalina
Also known as: hyaline, glassy cartilage, perichondrium
The most common cartilage: a glassy, avascular matrix of type II collagen and water-binding aggrecan, with chondrocytes in lacunae, that provides smooth, resilient support and the template for most of the fetal skeleton.
Overview
The matrix appears homogeneous ("glassy", Greek hyalos) because its fine type II collagen fibrils have the same refractive index as the ground substance. It is ≈60–80 % water, held by huge aggrecan aggregates (chondroitin and keratan sulfate on core proteins, attached to hyaluronan) whose negative charges draw in water — giving resilience to compressive loads, with the water squeezed out and drawn back like a sponge. Chondrocytes sit in spaces (lacunae) singly or in isogenous groups (clusters derived from one cell by division). The matrix immediately around each group (territorial matrix) is richer in GAGs and more basophilic than the interterritorial matrix.
Cartilage is avascular, aneural and alymphatic: chondrocytes receive nutrients by diffusion through the matrix from vessels in the perichondrium (or from synovial fluid in articular cartilage). The perichondrium has an outer fibrous layer (dense irregular connective tissue) and an inner chondrogenic layer containing progenitors. Cartilage grows by appositional growth (new chondroblasts from the perichondrium add matrix to the surface) and interstitial growth (chondrocytes divide within the matrix). Articular cartilage and the epiphyseal plates lack a perichondrium. Hyaline cartilage forms the model for endochondral ossification of most bones and the growth plates that lengthen them; it tends to calcify with age.
- Location
Articular surfaces of synovial joints; costal cartilages; nasal septum and alar cartilages; most laryngeal cartilages (thyroid, cricoid, most of arytenoid); tracheal and bronchial rings; epiphyseal plates; fetal skeleton.
Parts & subdivisions
- Matrix-producing cells; isogenous groups.
- Territorial and interterritorial matrixGAG-rich capsule around lacunae vs paler matrix between groups.
- PerichondriumFibrous + chondrogenic layers; source of appositional growth and nutrients.
- Specialised hyaline cartilage without perichondrium; zonal collagen arcades.
Anatomy
- Histology
Pale blue-purple homogeneous matrix (basophilic because of sulfated GAGs), more intense around lacunae; chondrocytes in lacunae, often in pairs or groups of four; perichondrium as a pink fibrous layer at the edge.
Function
- Smooth, low-friction articular surfaces that absorb compressive loads.
- Flexible support (nose, larynx, trachea, ribs).
- Template for endochondral bone formation and longitudinal bone growth (growth plate).
Clinical significance
Osteoarthritis
Degeneration of articular cartilage (loss of proteoglycan, fibrillation, erosion) with subchondral sclerosis and osteophytes; limited repair because cartilage is avascular and chondrocytes divide little — defects heal with inferior fibrocartilage.
Achondroplasia
Autosomal dominant gain-of-function FGFR3 mutation inhibits chondrocyte proliferation in growth plates → disproportionate short stature (rhizomelia) with normal intelligence; most cases are new mutations linked to advanced paternal age.
Calcification and chondrosarcoma
Laryngeal and costal cartilages calcify (and may ossify) with age, visible on radiographs. Chondrosarcoma is a malignant cartilage-forming tumour of adults (pelvis, proximal femur, shoulder).
Compiled from standard anatomy and physiology references — see the Cells & Tissues sources. For education only; not medical advice.