A proposed mechanism for the early development of the human tracheobronchial tree

Abstract

The development of the lung in 25 human embryos and early fetuses up to 140 mm crown-rump length was studied by examination of serial histologic sections, morphometry, and selected reconstructions. The proportion of pulmonary tissue consisting of tracheobronchial tree increases during this period. Bronchial cross-sectional diameter, length of the most distal bronchial branches, and thickness of the distal mesenchyme decline during development. The results are consistent with the concept that the dichotomous branching of the growing tracheobronchial tree occurs because of resistance to forward growth f the bronchial branch by compresses mesenchyme, pleura, or adjacent structures. Division and further growth of the bronchus takes place in areas of lower resistance. This process produces a "filling in" of space available for lung development and brings the epithelial and mesenchymal elements into their definitive relationships.

Association Between Tetralogy of Fallot and Tracheobronchial Branching Abnormalities: A New Clue for Pathogenesis?

“…Development of the tracheobronchial tree also begins early in fetal life, but the tracheobronchial epithelium originates from the endoderm. On gestational day 24, lung development begins as a ventral wall diverticulum of the foregut and then the endoderm undergoes a series of dichotomous and lateral branching to produce the conducting airways . These events occur during the embryonic (weeks 5–7) and pseudoglandular (weeks 5–17) phases.…”

“…These events occur during the embryonic (weeks 5–7) and pseudoglandular (weeks 5–17) phases. At day 36, segmental buds are already present . Thereafter, at the end of the sixth week, the branching pattern of lobar and segmental portions of the airway tree is established .…”

Congenital tracheobronchial stenosis in monozygotic twins

“…Nevertheless, since the patterns of the major branches are consistent, they must be controlled by ®xed developmental programmes. For the past few decades, normal bronchopulmonary development was divided into ®ve phases by many authors [4,6,10,13]. Weeks 4±6 are crucial in the development of proximal airways, and the conducting airways develop during weeks 7±16 of the embryo.…”

“…It is generally believed that tracheobronchial malformations are the result of a defect or arrest in the development of the foregut at stages 13±15 of embryonic development at around 4±6 weeks [4,6,10,13]. In many instances, tracheobronchial abnormalities are part of a syndrome with dierent modes of inheritance [2], however, the real cause of such anomalies remains elusive.…”

Distribution of Integrins During Human Fetal Lung Development

“…During the pseudoglandular stage, a period from Week 7 to Week 16 of development (WD), the tracheal rudiment undergoes repeated dichotomous divisions. This process of branching morphogenesis leads to the formation of the entire bronchial tree (Hutchins et al 1981). After 11 WD, gland development begins from surface epithelial cell buds which invade the underlying mesenchyme (Thurlbeck et al 1961).…”