Structure of elastin. Illustration of the structure of the protein elastin, as found in the connective tissue of arteries, skin and ligaments. Across top, the cross-links between individual elastin molecules is shown in its stretched form. When the tension is released, the fibre relaxes and contracts as shown at bottom. This cycle of relaxation and stretching can be repeated. Elastin is one of the proteins that gives skin its elasticity. For this artwork without labels, see image C023/8716.