embryonic period, the earliest period or phase of lung development in utero, lasting from the third week after conception to the sixth week. It is sometimes not named as a defined period of lung development, which is instead considered to begin with the following pseudoglandular period. During this period, a ventral respiratory diverticulum (lung bud) arises from the caudal end of the laryngotracheal groove and grows into bronchial buds and the primordial trachea. Also called embryonic phase.
