The microarchitecture of collagen fibrils in the articular disc of the temporomandibular joint (TMJ) plays an important role in dissipating the mechanical load during jaw movement. However, little information is available on its adaptations to the biomechanical environment during development. To address this issue, we analyzed the diameter of collagen fibrils of the articular disc of the rat TMJ with quantitative ultrastructural analysis during postnatal development. The mean diameter of the collagen fibrils significantly increased and the arrangement of the collagen fiber networks became compact during development. Articular discs of suckling rat pups were composed of thin, uniformly sized collagen fibrils (range: 30-60 nm, peak: 40-50 nm). At the age of 4 weeks, thicker collagen fibrils began to appear in articular discs, shortly after weaning (range: 20-70 nm, peak: 40-50 nm). In articular discs of adult rats, collagen fibrils varied widely in diameter, with thick fibrils predominating (range: 10-120 nm, peak: 40-70 nm). These age-related changes in the microarchitecture of collagen fibrils in articular discs may reflect changes in their biomechanical environment during development.
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