Page 674 - Atlas of Histology with Functional Correlations

In the lung, the surrounding hyaline cartilage rings of the trachea are

replaced by cartilage plates (11, 14). A perichondrium (12, 15) covers each
cartilage plate (11, 14) as they become smaller and farther apart as the bronchi
continue to divide and decrease in size. Between the cartilage plates (11, 14), the
submucosa (8) blends with the adventitia (3). Bronchial glands (5, 18) and
adipose cells (2) are present in the submucosa (8) of larger bronchi.

Bronchial blood vessels (19) and a bronchial arteriole (4) are in the
connective tissue around the bronchus. Accompanying the bronchus are also a
larger vein (9) and an artery (17).

Surrounding the intrapulmonary bronchus, its connective tissue, and the

hyaline cartilage plates (11, 14) are the lung alveoli (1, 13).

FIGURE 17.12 ■ Intrapulmonary bronchus (transverse section). Stain:

hematoxylin and eosin. Low magnification.

FIGURE 17.13 | Intrapulmonary Bronchus,

Cartilage Plates, and Surrounding Alveoli of Lung

This medium-power micrograph of a small, intrapulmonary bronchus cut in
cross section shows the cartilage plates (5, 9) around its lumen (2). The
respiratory epithelium (1) of ciliated and goblet cells lines the lumen of

bronchus (2). Surrounding each cartilage plate (5, 9) is the perichondrium (3).
Located below the respiratory epithelium (1) is a layer of smooth muscle (7)
that encircles the bronchus and controls its diameter during respiration. In the

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