Cartilage - structure and function, description of individual types

Introduction

Cartilage is a flexible connective tissue with important roles in support, cushioning and serving as a template for bone formation. It is avascular, so nutrients diffuse through the matrix. All types share chondrocytes in lacunae and collagen-rich ECM, but each type has its special features.

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General Structure

• Chondrocytes – mature cartilage cells living in lacunae
• ECM – collagen fibres + proteoglycans (very hydrophilic, makes cartilage resistant to compression)
• Perichondrium – fibrous outer layer in most cartilages (except articular cartilage and fibrocartilage)

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1. Hyaline Cartilage

Appearance

Glassy, smooth, bluish matrix. Collagen type II fibres are present but hard to see.

Location

• Articular surfaces
• Nose, trachea, bronchi
• Foetal skeleton (template for endochondral bone)

Function

• Low-friction surface in joints
• Flexible support
• Model for bone formation in embryos

ECM Feature

High water content → good shock absorption.

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2. Elastic Cartilage

Appearance

Similar to hyaline but contains elastic fibres, which are dark and visible in special stains.

Location

• External ear (auricle)
• Epiglottis
• Auditory tube

Function

• Flexible support that can withstand bending
• Always returns to its original shape

ECM Feature

Elastic fibres give it “springy” behaviour.

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3. Fibrocartilage

Appearance

Strongest cartilage. Has thick type I collagen bundles → looks like a mix of tendon and cartilage.

Location

• Intervertebral discs
• Pubic symphysis
• Menisci of knee

Function

• Resist compression + tension
• Shock absorption in high-stress joints

ECM Feature

No perichondrium; collagen fibres arranged in parallel bundles.

Bibriography

Junqueira

RNDr. Lucie Fraser Lantová, Ph.D. HYALINE, ELASTIC

AND FIBROCARTILAGE