This page shows ventral views of the esophagus and developing lungs, accompanied
by cross-sectional views through the area between the black arrows. Note how the
lung starts as an evagination, from the esophogeal endoderm, called the larygotracheal
groove (1). As the the larygotracheal groove grows, it develops two outcroppings
at its caudal end, the lung buds (2). As the lung buds grow, they branch repeatedly
forming the primary bronchi and stem bronchi (3) which branch further to form
bronchioles, which will eventually develop terminal air sacs (alveoli) to complete
the adult lung. Also, note how the trachea, once attached as a ventral groove
on the esophagus, has separated to become a distinct tube (3).
Special thanks to Hans Christoffersen for the
preparation of this page.
Send comments to:
Sandra K. Ackerley (),
Department of Zoology, University of Guelph, Guelph, Ontario,
Canada N1G 2W1.