Page 671 - Atlas of Histology with Functional Correlations

excretory duct (5) of the tracheal glands (3) is lined with a simple cuboidal

epithelium and extends through the lamina propria (11) to the epithelial surface
(8).

The hyaline cartilage (1) is surrounded by perichondrium (2). The larger
chondrocytes in lacunae (4) that are located in the interior of the hyaline
cartilage (1) become flatter toward the perichondrium (2) that blends with the

submucosa (6). An arteriole and a venule (12) supply the connective tissue of
the submucosa (6) and the lamina propria (11).

FIGURE 17.10 ■ Tracheal wall (sectional view). Stain: hematoxylin and eosin.
Medium magnification.

FIGURE 17.11 | Lung (Panoramic View)

This low-magnification illustration shows the major structures in the lung for air

conduction and gaseous exchange (respiration).

The histology of the intrapulmonary bronchi is similar to that of the trachea
and extrapulmonary bronchi, except that in the intrapulmonary bronchi, the C-
shaped cartilage rings of the trachea are replaced by cartilage plates. All cartilage
in the trachea and lung is hyaline.

The wall of an intrapulmonary bronchus (5) can be identified by the

presence of hyaline cartilage plates (7). The wall (5) also consists of lamina
propria (4), a layer of smooth muscle (3), a submucosa (2) with bronchial
glands (6), hyaline cartilage plates (7), and an adventitia (1). The surface of a

bronchus (5) is also lined with a pseudostratified columnar ciliated epithelium
with goblet cells.

As the intrapulmonary bronchus (5) branches into smaller bronchi and
bronchioles, the epithelial height and the cartilage plates around the bronchi
decrease until an occasional piece of cartilage is seen. Cartilage disappears from

the bronchi walls when their diameters decrease to about 1 mm.

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