Created using ZBrush, Maya, and Adobe After Effects to be used in the Embryology course at the University of Dundee
At the start of the fourth week or 22 days, the lung bud is visible​ emerging from the endodermal foregut as shown on the right.
During the fourth week from 26 to 28 days, the lung bud splits into primary bronchial buds.
During this time on the left, a cross section view through the point of connection between the lung bud and endoderm shows the tracheoesophageal ridge as it forms the tracheoesophageal septum and then separates into the trachea and esophagus​.
During the fifth week, secondary bronchial buds can be seen forming on the right.
During this time on the left, a cross section at the level of the heart shows the primitive pericardial cavity separate into the pericardial cavity and two pleural cavities.
During the sixth week, the formation of tertiary bronchial buds can be seen on the right. The seventh and eighth weeks show two further generations of bronchial branching.