Luisa Vera MD Médico Radiólogo Radiologist Caracas, Venezuela February 17 -2022 DEVELOPMENT OF THE LOWER RESPIRATORY SYSTEM Development of the lower respiratory tract begins on day 22 and continues to form the trachea, lungs, bronchi, and alveoli. The process divides into five stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar stage. Although the process begins early on in fetal development, complete maturation does not take place until the child is approximately 8 years of age. This developmental delay is vital in premature babies where their survival is intricately linked to which developmental stage their respiratory tract has reached at the time of birth. Embryonic Stage – 3-6 weeks The respiratory diverticulum appears on the ventral wall of the primitive foregut endoderm, posterior to the pharynx. Following the fourth week of development, the caudal end of the trachea bifurcates to form the left and right primary bronchial buds which continue ...