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Know your nose
The nasal cavity is divided into two passages by the
nasal
septum. The nasal septum is composed of both bone and
cartilage and extends from the nostrils to the back of the
throat. Bones called nasal conchae project into the
lateral walls of the nasal cavity, forming a series of
folds called turbinates. There are three turbinates on
each side of the nasal cavity and are lined by a thick
mucous membrane. Turbinates greatly increase the surface
area of the nasal cavity. During inhalation air is
directed over and under the turbinates.
Lining the nasal cavity is a mucous membrane rich with
blood vessels. As air passes over the nasal mucosa it is
prepared and conditioned to safely pass deeper into the
respiratory system and ultimately end up in the lungs.
The
heat radiated from the blood vessels warms the air to near
body temperature. Simultaneously, watery
mucous is
secreted humidifying the air and trapping foreign
particles. The increased surface area provided by the turbinates aids this processes to be performed quickly.
Cells in the mucous membrane have tiny hair-like
projections called cilia. Usually, the mucus traps
incoming dirt particles, which are then moved by the
cilia; in coordinated waves, they sweep a layer of mucus
to the back of the nose every 5-8 minutes. The mucus then
moves toward the front of the nose or slips into the
throat where it is swallowed, rather than inhaled into the
lungs. The acid of the stomach destroys the harmful nasal
debris.
Unfortunately, there are some conditions that cause the
cilia to stop working. The cilia can be paralyzed most of
all by infection but also by factors such as cold
temperatures, cigarette smoke, some medications (e.g.
antihistamines), or by excess dryness. When the cilia do
not work well, we have trouble with nasal crusting and
sinus infections. It has been demonstrated by numerous
scientific studies that cilary activity can be improved by
salty water.
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DID YOU KNOW:
the cilia in our noses beat 400-800 times
each minute! |
The nasal mucosa which lines the roof of
the nasal cavity and the superior turbinates is
structurally modified to detect odor-producing chemicals.
On its surface layer, are millions of specialized nerve
cells called olfactory (nasal) receptors.
Several open air-filled chambers called paranasal sinuses
(Frontal, Ethmoid, Maxillary) are present in the bones
surrounding the nasal cavity. The air-filled sinuses help
lighten the skull and resonate the voice sounds. Like the
nasal cavity, the sinuses are lined with a mucous membrane
composed of cells that produce mucus and have cilia.
Incoming dirt particles are trapped by the mucus, and then
moved by the cilia into the nasal cavity, through small
sinus openings. Because these openings are so small, the
drainage can easily be blocked by conditions such as colds
or allergies, which produce swelling of the mucous
membranes. Blockage of normal sinus drainage leads to
sinus inflammation and infection (sinusitis).
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