How do elastic and collagen fibres support the walls of alveoli?

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Illustration showing different animals and their respiratory organs: a spider with book lungs, a chicken with lungs, a sponge with labeled inflow and outflow pores, a fish with gills, and a caterpillar with spiracles. — Respiratory system Different methods of respiration in animals.

The walls of the pulmonary alveoli are supported by a meshlike fabric of elastic fibres and collagen fibres that weaves between the capillaries. These fibres provide essential structural integrity to the gas-exchange region:12

Collagen fibres: Because they are more rigid, these fibres provide the necessary firmness to the alveolar wall.1
Elastic fibres: These fibres allow the alveolar walls to expand and contract during the process of breathing.1

This fibre system is interwoven with the capillaries and is particularly reinforced at the alveolar entrance rings, helping to maintain the stable supporting framework required for efficient gas exchange.2