This connective tissue contains collagen fibers for flexibility and strength, and numerous elastic fibers that enable it to be stretched. Alveolar connective tissue is found in the skin and in most internal organs of vertebrates, where it allows the organs to expand, which is essential for the lungs.his connective tissue contains collagen fibers for flexibility and strength, and numerous elastic fibers that enable it to be stretched. Alveolar connective tissue is found in the skin and in most internal organs of vertebrates, where it allows the organs to expand, which is essential for the lungs.