Abnormal pleura morphology Abnormal pulmonary fissure morphology 2020-05-07T07:12:18Z An abnormal form or number of the pulmonary fissures. A fissure is the infolding of visceral pleura that separates one lobe or part of a lobe from another; thus, the interlobar fissures are produced by two layers of visceral pleura. The azygos fissure, unlike the other fissures, is formed by two layers each of visceral and parietal pleura. Supernumerary fissures usually separate segments rather than lobes. Supernumerary fissures usually separate segments rather than lobes. Abnormal lung development