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Elastic fibers are components of the extracellular matrix composed of elastin protein that enable tissues like skin, lungs, and blood vessels to stretch and recoil. These fibers confer remarkable tissue elasticity, allowing tissues to return to their original shape after being stretched or compressed, which is essential for proper tissue function.

Elastin is composed of tropoelastin molecules with alternating hydrophobic and cross-linking domains. Hydrophobic motifs cover over 80 percent of the protein, enabling elastin to self-associate, stretch, and recoil. Cross-linking domains form bonds between neighboring tropoelastin molecules, creating fibers that can stretch more than fivefold compared to rubber bands.

As elastic fibers mature, tropoelastin aggregates form an amorphous core surrounded by microfibrils. This mature structure combines the elastin aggregates with supporting microfibrils, creating the final elastic fiber architecture that provides tissues with their characteristic ability to stretch and return to original shape.

Elastic fibers are prominent in elastic tissues including skin, elastic ligaments of the vertebral column, vocal folds, and arterial walls. Dense irregular elastic tissue in arterial walls provides strength and allows blood vessels to regain their original shape after stretching. Elastic cartilage in the external ear also contains elastin fibers alongside collagen and proteoglycans.

Hydrophobic motifs in elastin allow the protein to self-associate and enable stretching and recoiling, while cross-linking domains form covalent bonds between neighboring tropoelastin molecules. Together, these complementary structural features create elastic fibers with exceptional mechanical properties that far exceed the elasticity of synthetic materials like rubber.

While the transcript does not explain the mechanism of age-related elasticity loss, the overview notes that elasticity of tendon tissue decreases with age, putting older adults at risk for tendinitis. This age-related change affects tissues containing elastic fibers, though the specific molecular basis for this decline is not detailed in the source material.

Dense regular elastic tissue contains both elastin fibers and collagen fibers, allowing ligaments to return to their original length after stretching. While elastin provides elasticity and recoil, collagen provides structural support. Together, these proteins work synergistically in tissues like ligaments and arterial walls to balance strength with flexibility.