Figure 7-4. Infralaryngeal structures.
In the center of the thorax, the trachea divides into right and left primary bronchi.
The right is somewhat more vertical than the left. Therefore, when a person
accidentally aspirates ("breathes in") a foreign object, it is more likely to be found in the
right primary bronchus than the left.
a. Each primary bronchus extends laterally into the substance of the appropriate
lung. Within each lung, the tubular structure divides, subdivides, and divides again, up
to about 30 times. Thus, the tubes become more and more numerous and smaller and
smaller in size. At the terminals of the branching tubes are groups of spherical alveoli.
This gives the appearance of a bunch of grapes.
b. A variety of situations may occlude (close or shut off) these tubular air
(1) A foreign object may be aspirated ("breathed in").
(2) The wall of the tube may constrict in a bronchial spasm.
(3) The lining of the tube may become swollen with fluid and close the