Development of the Intrasegmental Bronchial Tree: the Pattern of Branching and Development of Cartilage at Various Stages of Intra-uterine Life
Year: 1961
Type: article
Abstract: The purpose of this study is to establish the progress of branching of the intrasegmental part of the bronchial tree at different phases of intra-uterine life and the relation to it of the develop-ment of bronchial cartilage. The importance of the topography of the pulmonary segments to both the surgeon and the clinician has led in recent years to the study of the growth of the segmental structures (Boyden, 1955), and, in order to establish that post-natally new branches of the bronchial tree appear, the most peripheral parts of the respiratory system have previously also been studied (e.g., Willson, 1928). But there is little published work describ-ing the development of the region in between, i.e., the intrasegmental bronchi and bronchioli. INTRASEGMENTAL BRANCHING In the five-week foetus (crown-rump length of 8 to 10 mm.) the lobar bronchi are present as small outgrowths from the two primary stem bronchi (Heiss, 1919). Boyden (1955) has described the way in which, in a "burst of activity, " these lobar bronchi subdivide so that segmental bronchi are recognizable from the sixth week. During the weeks following, the appear-ance of the lung is commonly described as "glandular, " because its air spaces are enclosed by epithelium surrounded by solid mesenchyme, i.e., the bronchial tree is blind at its distal end and completely lined by epithelium. Increasing vascu-larization and differentiation into hollow alveoli gives rise to what is known as the " canalicular " phase, which lasts from the sixteenth to the
Source: Thorax
DOI: 10.1136/thx.16.3.207
Authors: U. Bucher, L. Reid
Institution: Royal Brompton Hospital
Language: English
Subfield: Pulmonary and Respiratory Medicine
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2129108051