6 Retinoic Acid Signaling and Development of the Respiratory System
155
Fig. 6.1 Schematic outline of lung development in human, monkey, sheep, rabbit, rat, and mouse
Once the Nkx2.1-expressing cells are specified in the prospective lung field, they
undergo proliferation to form trachea and the two primary lung buds (Fig. 6.2). Primary lung buds form at E9.5 in mice (5 gestational weeks in humans), and the trachea
begins its separation from the esophagus (Warburton et al. 2010). Toward the end
of the embryonic phase, the mesenchymal cells surrounding the trachea condense
focally and differentiate into cartilage progenitors (Schittny 2017).
The pseudoglandular phase (E12 to E116.5 in mice, 5–17 gestational weeks in
humans) is characterized by the outgrowth of the terminal bud into the surrounding
155
Fig. 6.1 Schematic outline of lung development in human, monkey, sheep, rabbit, rat, and mouse
Once the Nkx2.1-expressing cells are specified in the prospective lung field, they
undergo proliferation to form trachea and the two primary lung buds (Fig. 6.2). Primary lung buds form at E9.5 in mice (5 gestational weeks in humans), and the trachea
begins its separation from the esophagus (Warburton et al. 2010). Toward the end
of the embryonic phase, the mesenchymal cells surrounding the trachea condense
focally and differentiate into cartilage progenitors (Schittny 2017).
The pseudoglandular phase (E12 to E116.5 in mice, 5–17 gestational weeks in
humans) is characterized by the outgrowth of the terminal bud into the surrounding