27.5
Elastin is Responsible for Tissue Elasticity
Elastic fiber contains the protein elastin along with lesser amounts of other proteins and glycoproteins. The main property of elastin is that it will…
Tissues such as skin, lungs, and blood vessels must be strong as well as elastic to work properly. Tissues owe their elastic properties to the elastic fibers present in their extracellular matrix.
Each of these fibers is composed of tropoelastin aggregates assembled on the microfibrils.
Tropoelastins are the precursors of elastin molecules, made up of alternating hydrophobic and cross-linking domains.
The hydrophobic motifs, which cover more than 80 percent of the total protein, allow elastin to self-associate, stretch, and recoil when needed. The cross-linking domains allow cross-links to form between neighboring tropoelastin molecules.
Together, these structural features allow fibres to stretch more than fivefold compared to a rubber band of a similar cross-section.
As elastin fibers mature, the elastin aggregates form an amorphous core surrounded by microfibrils. These elastin structural features confer remarkable tissue elasticity.
View the full transcript and gain access to JoVE Core videos
Q1: What are elastic fibers and why do tissues need them?
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.
Q2: How is elastin structured at the molecular level?
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.
Q3: What happens to elastic fibers as they mature?
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.
Q4: Where are elastic fibers found in the body?
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.
Q5: How do hydrophobic and cross-linking domains work together in elastin?
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.
Q6: Why does elasticity decrease with age in connective tissues?
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.
Q7: What is the relationship between elastin and collagen in connective tissues?
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.