The respiratory system begins its development in the fourth week from a single respiratory diverticulum of endoderm from the ventral surface of the esophagus (foregut). ▪ The respiratory diverticulum lengthens to form the lung bud. ▪ The lung bud then bifurcates into two bronchial (lung) buds. ▪ The bronchial buds continue to divide through a series of divisions over time to develop into the respiratory tree. ▪ Since the respiratory system develops from the foregut, initially there is an open communication between the trachea and the foregut. ▪ This communication is closed by the growth of a mesodermal septum called the tracheoesophageal septum. ▪ A tracheoesophageal fistula is an abnormal opening that occurs between the trachea and esophagus as a result of an abnormal development of the tracheoesophageal septum. help me in making systematic notes for revision and easy to understand without missing any point also for better visul understanding create visual images to make concept clear