Respiratory Tract
SH1
Lesson objective
• Describe the structure of the human gas exchange system.
• Describe the distribution in the gas exchange system of cartilage,
ciliated epithelium, goblet cells, squamous epithelium of alveoli,
smooth muscle and capillaries.
• Recognise cartilage, ciliated epithelium, goblet cells, squamous
epithelium of alveoli, smooth muscle and capillaries in
microscope slides, photomicrographs and electron micrographs.
LARYNX
Vocal folds
PSEUDOSTRATIFIED CILIATED EPITHELIUM
Basement membrane trachea
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The innermost cells of the trachea are the
ciliated epithelia with projections called
cilia
The cells of the ciliated epithelium are
shown here – the cells are tightly packed
and interspersed with goblet cells, which
are shown in purple
The cilia are essential for sweeping bacteria
and dust-filled mucus away from the lungs
and up the trachea into the back of the
mouth
This mucus is then swallowed, with any
pathogens hopefully destroyed by the acidic
conditions in the stomach
BRONCHUS AND BRONCHIOLE
In A, part of a bronchus can be seen.
• Bronchi are lined by pseudostratified columnar epithelium
with goblet cells.
• The thickness and layering of the epithelium decreases
gradually with the decrease in the size of the bronchi.
• A smooth muscle layer encircles a thin connective tissue
lamina propria.
• In contrast to the trachea, the smooth muscle of the bronchus
is arranged in interlacing spirals around the bronchus.
• Between the smooth muscle layer and the cartilage is the
submucosa, which may contain seromucous glands, not seen
in this preparation.
• The hyaline cartilage is arranged in discontinuous plates
around the bronchus.
BRONCHUS AND BRONCHIOLE
In B
• A bronchiole is seen in the midst of respiratory tissue.
• The epithelium is simple columnar ciliated.
• The lamina propria is replaced by the muscle layer that
encircles the bronchiole. in man, cartilage and glands are
characteristically present until bronchioles decrease in size to
approximately 0.5 mm in diameter.
ALVEOLAR DUCT AND ALVEOLAR SACS
Alveolar duct: Arises by branching of respiratory bronchioles;
wall made up of alveolar sacs and alveoli. Lining epithelium is
reduced to flattened cells with occasional cuboidal cells.
Alveolar sacs: Cluster of alveoli that open into the lumen of
the alveolar duct. Individual alveoli are lined by thin
squamous cells (Pneumocyte 1) and cuboidal cells that bulge
into the alveolus (Pneumocyte II). The latter cell is responsible
for the production of surfactant, which maintains the
configuration and stability of the alveolus and plays a role in
fluid transport across the alveolocapillary membrane. Site of
respiratory exchange.
ALVEOLUS
Conclusion
Thank You