Page 686 - Atlas of Histology with Functional Correlations

bronchi

Bronchioles of about 1 mm diameter no longer have cartilage plates
As tubular size decreases, epithelium becomes simple ciliated and goblet
cells disappear

Clara Cells

Replace goblet cells and become predominant cells in terminal and
respiratory bronchioles
Are secretory, nonciliated cells that increase in number as ciliated cells
decrease

Secrete surfactant-like lipoprotein components that break down mucus
stickiness and reduce surface tension
Also function as stem cells to replace lost or injured bronchial epithelial cells

Secrete proteins and lysozymes into bronchial tree to protect lung from
inflammation or toxic pollutants

Respiratory System—Respiratory Portion

Starts with a passageway where initial respiration can take place
Terminal bronchioles give rise to respiratory bronchioles, a transition zone
for respiration

Respiratory bronchioles exhibit thin-walled alveoli, where gaseous exchange
takes place
Gaseous exchange can take place only when alveoli are present

Alveoli are final airspaces and are surrounded by capillary plexus for gaseous
exchange
Consists of respiratory bronchioles, alveolar ducts, alveolar sacs, and alveoli
Goblet cells are absent from alveoli and the lining is very thin where
respiration occurs

Cells of Lung Alveoli

Type I alveolar cells (type I pneumocytes) are very thin that line the lung
alveoli

Capillary endothelium and type I alveolar cells form the thin blood–air

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