The Common Vein Copyright 2008

Joshua Namias MD

Early in development, the esophagus, oropharynx, larynx, trachea, bronchi, and lungs derive from a common tube comprised of endoderm.  At 4 gestational weeks the respiratory components differentiate from a diverticulum off this common system.  A second “bud” of this common structure forms into the foregut.  This primitive foregut grows with its columnar epithelium, destined to form the digestive tract.  Over several weeks, this growth continues with many changes along the way.  The columnar epithelium, which remains in the more distal GI tract, starts to change to squamous mucoa at week 16 an continues until birth