Journal of Basic and Applied Research International

Introduction: During gestation period the fetal lung undergoes significant morphological changes to provide at birth an organ capable of maintaining respiration and gas exchange. Although lung development is continuous during embryogenesis, five developmental stages have been delineated, based on anatomic and histologic characteristics. With the aim to understand the histological differences during the embryogenesis, we conducted a descriptive study to analyse the different components of fetal lung.

Materials and Methods: The present study was carried out on 15 human fetuses of known gestational age (GA) in the department of Anatomy, Kasturba Medical College Manipal. The lungs were resected and the tissues were processed for histological observations. The sections were stained using Hematoxylin and Eosin stain.

Results: In first trimester the lung showed the sections of intrapulmonary bronchi and varying sizes of bronchioles. The intrapulmonary bronchus was lined by pseudostratified ciliated columnar epithelium surrounded by immature hyaline cartilage. Bronchioles were lined by cuboidal to columnar epithelium. No prominent blood vessels were observed.  In second trimester the well developed blood vessels were observed adjacent to it. The hyaline cartilage surrounding it showed some signs of maturity by 16 weeks. In third trimester all the components of the lung were well developed and the glandular components were observed. The bronchioles were well differentiated into terminal and respiratory bronchioles with saccular outpouchings of alveoli.

Conclusion: The present study explains the histogenesis of the fetal lungs according to the GA which is an essential aspect in the embryological and clinical domain.