The olfactory epithelium is located within the nose. The epithelium contains olfactory
receptors, several supporting cells, and neurons of the olfactory nerves.
Structures of the olfactory epithelium • Figure 8.4
Olfactory
tract
Olfactory
epthelium
Sagittal view
Olfactory gland -
produces mucus.
Basal cell - a stem cell
that has undergone division
and differentiation to form a
new olfactory receptor.
Supporting cell - columnar v
epithelial cell that supports
receptor in the following ways:
• Physical support
• Nourishment
• Electrical insulation
• Detoxification of chemicals
that contact epithelium
Mucus secretion:
Olfactory bulb
Olfactory bulb
neuron
Parts of olfactory (I) nerve
Cribriform plate
Bundle of axons of
olfactory receptors
Connective tissue
Developing olfactory
receptor
- incomplete
receptor whose dendrite
has not reached mucus.
Olfactory receptor -
neuron that detects
odorants in its olfactory
hairs (cilia).
Odorants
- chemicals
that stimulate the
olfactory hairs of
.
. ,
olfactory receptors.
• moistens epithelium
• dissolves/traps odorants
Enlarged aspect of olfactory receptors
Olfaction, like all the special senses, has a low thresh-
old. As little as a few molecules of certain substances can
be detected in the air. A good example is the chemical
methyl mercaptan, which smells like rotten cabbage and
can be detected in very low concentrations. Because nat-
ural gas is odorless, but a leak is potentially lethal, this
chemical is added in very small amounts to the natural gas
used for cooking and heating.
Some Special Senses Use Receptors That Detect Chemicals
233
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