The [BLANK-1] descends through the thorax and ends at the [B…
The descends through the thorax and ends at the , where it divides into the right and left . Each bronchus enters a lung and then branches into — on the right and on the left. They then divide into which continue bifurcating into . The last division of the previous structure forms the , which give rise to that mark the beginning of the respiratory zone. The next bifurcation forms , which lead into clusters of where gas exchange occurs.