Microanatomical Studies on the Broncho-pulmonary Segments of Lungs in Domestic Pig (Sus scrofa domesticus)

Abstract

The study was conducted from December, 2020 to May, 2021 in the Department of Veterinary Anatomy, College of Veterinary Science, Rajendranagar, Hyderabad, India to provide a thorough description of the histological characteristics of the broncho-pulmonary segments of domestic pig lungs, given the structural similarities between human and pig lungs and the significance of this species as an experimental model for biomedical research. A typical broncho-pulmonary segment was composed of the following histological structures: segmental bronchi, primary, secondary, and tertiary bronchioles and their branches, all of which terminated in an alveolar duct or a cluster of alveoli. Each broncho-pulmonary segment was accompanied by a matching artery to the tiniest divisions of the bronchial tree. Lamina mucosa, sub-mucosa, and outer adventitia were the three layers of secondary (lobar) bronchi. Mucosal layer was lined by pseudo-stratified ciliated columnar epithelium; the sub-mucosal layer was made up of a hyaline cartilage layer and a stretch of sub-mucosal glands and blood vessels. Segmental bronchi epithelium was simple columnar, stratified cuboidal while cuboidal in terminal bronchioles. The terminal bronchioles had a folded mucosa, formed of small strands of collagen and smooth muscle fibres. Terminal bronchioles were linked to alveolar ducts, which in turn were linked to a spate of alveoli with squamous epithelium.