Elastic connective tissue

Elastic fibres consist of an amorphous core of elastin — a hydrophobic protein rich in glycine, proline and alanine, cross-linked by the unique amino acids desmosine and isodesmosine (via copper-dependent lysyl oxidase) — surrounded by a scaffold of fibrillin microfibrils. Like a rubber band, they can stretch to ≈150 % of their resting length and recoil passively. They appear yellow when fresh and are poorly stained by eosin; Verhoeff, orcein or resorcin-fuchsin stains demonstrate them.

In the elastic (conducting) arteries — aorta, pulmonary trunk and their large branches — elastin forms ≈40–70 concentric fenestrated elastic lamellae in the tunica media, made by smooth-muscle cells rather than fibroblasts. They store energy during systole and recoil during diastole, damping pulsatile flow and maintaining diastolic pressure (Windkessel effect). Elastic ligaments — the ligamenta flava joining vertebral laminae, the vocal ligaments and the suspensory ligament of the penis — and the elastic network of the lungs and bronchial tree allow structures to return to shape after stretching. Lung elastic recoil drives passive expiration.