NOSE
Nose, organ of
smell, and also part of the apparatus of respiration and voice. Considered
anatomically, it may be divided into an external portion—the visible projection
portion, to which the term nose is popularly restricted—and an internal
portion, consisting of two principal cavities, or nasal Fosse, separated from
each other by a vertical septum, and subdivided by spongy or turbinated bones
that project from the outer wall into three passages, or meat uses, with which
various sinuses in the ethmoid, spheroid, frontal, and superior maxillary bones
communicate by narrow apertures.
The margins of the nostrils are usually lined
with a number of stiff hairs that project across the openings and
serve to arrest the passage of foreign substances, such as dust and small
insects, which might otherwise be drawn up with the current of air intended for
respiration. The skeleton, or framework, of the nose is partly composed of the
bones forming the top and sides of the bridge, and partly of cartilages. On
either side are an upper lateral and a lower lateral cartilage, to the latter
of which are attached three or four small cartilaginous plates, termed sesamoid
cartilages. The cartilage of the septum separates the nostrils and, in
association posterior with the perpendicular plate of the ethmoid and with the
vomer, forms a complete partition between the right and left nasal Fosse.
Smell, one of the
five special senses by which odors are perceived. The nose, equipped with
olfactory nerves, is the special organ of smell. The olfactory nerves also
account for differing tastes of substances taken into the mouth, that is, most
sensations that appear introspectively as tastes are really smells.
Sensations of smell are difficult to describe and
classify, but useful categorizations have been made by noting the chemical
elements of odorous substances. Research has pointed to the existence of seven
primary odors—camphor like, musky, floral, pepper mint like, ethereal
(dry-cleaning fluid, for example), pungent (vinegar like), and
putrid—corresponding to the seven types of smell receptors in the
olfactory-cell hairs. Olfactory research also indicates that substances with
similar odors have molecules of similar shape. Recent studies suggest that the
shape of an odor-causing chemical molecule determines the nature of the odor of
that molecule or substance. These molecules are believed to combine with
specific cells in the nose or with chemicals within those cells. This process
is the first step in a series that continues with the transmission of impulses
by the olfactory nerve and ends with the perception of odor by the brain.