LUNG
Figure 19­18
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Holdings,
The conducting portion of the respiratory system bifurcates as it enters the lungs to form the bronchi. The bronchi
branch distally and their walls become thinner with the loss of cartilage plates and the presence of a more simplified
epithelium. The next division of the conducting portion is the muscular bronchioles, terminating in the respiratory
LLC.
bronchioles, which constitute the first area of the lungs where gas exchange occurs. As a result, respiratory bronchi-
Not
oles are the first division of the respiratory portion of the system.
to
be
The pulmonary arteries follow the bronchi and bronchioles, and sections through these structures often include these
redistributed
blood vessels. A respiratory bronchiole (arrow) and its accompanying pulmonary artery (arrowhead) are shown in
the center of the micrograph.
The open air spaces of the alveoli provide the main histologic clue in the identification of this organ. Well-preserved
or
tissue will ensure that these small airways are not collapsed. This imparts a lacy appearance to the organ at low
modified
magnifications.
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way
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1109

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