Page 658 - Atlas of Histology with Functional Correlations

Basal cells are located close to the basal lamina without their apices reaching

the lumen of the epithelium. These cells serve as stem cells for continual
replacement of other epithelial cells.

Brush cells are less numerous than the other cells. Because their basal
surfaces contact afferent nerve endings, it is believed that these cells function as
receptor cells.

Small granule cells (Kulchitsky cells) contain numerous membrane-bound

granules and are analogous to the enteroendocrine cells of the diffuse
neuroendocrine system (DNES).

Other cells are seen in the nasal cavity, in the bronchioles, and the alveoli.

OLFACTORY EPITHELIUM

Before entering the lungs, the air first passes through either the mouth or the
nasal cavity. Located in the superior and lateral regions in the roof of the nose

are the bony nasal shelves called conchae. Lining this selected region is a highly
specialized sensory pseudostratified epithelium called the olfactory epithelium
that detects and transmits odor sensations to the brain. This epithelium consists

of three major cell types: supportive (sustentacular), basal, and olfactory
(sensory). Located inferior to the epithelium in the lamina propria are the serous
olfactory (Bowman) glands. In contrast to the respiratory epithelium, the
olfactory epithelium lacks goblet cells or motile cilia on its cells.

Olfactory cells are the sensory bipolar neurons that are distributed

between the more apical supportive cells and the basal cells. The olfactory cells
span the thickness of the olfactory epithelium and end at the surface as small,
round bulbs called the olfactory vesicles. Radiating from each olfactory vesicle
are long, nonmotile olfactory cilia that lie parallel to the epithelial surface.

These cilia are nonmotile and function as sensory odor receptors. The bases of
the olfactory cells connect to axons that leave the epithelium through the
basement membrane, converge in the lamina propria below the epithelium to
form bundle of nerve fibers that pass through the ethmoid bone of the skull, and

synapse in the olfactory bulb of the brain (olfactory, or cranial nerve I).

In the olfactory epithelium are olfactory nerves, olfactory (Bowman) glands,
blood vessels, lymphatic vessels, and other cellular components of the
connective tissue. Olfactory (Bowman) glands produce a serous fluid that bathes

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