The nose is composed of two nasal cavities, or spaces,
separated by a middle wall, which is called the nasal septum. The nose warms,
humidifies, and filters the air you inhale, protecting the delicate tissues
within the lung.
On the outside walls of each nasal cavity is a
series of three smooth ridges, called turbinates. The turbinates can alter the
blood flow beneath their surface, thus increasing or decreasing their size,
which in turn regulates the flow of air through the nose. In addition, the
outer nasal cavity contains coarse hairs that trap large particles and prevent
them from passing into the deeper part of the nasal cavity.
See a
picture of the
nasal passage.
The sinuses, which are air-filled cavities behind
the nose in the cheeks and forehead, have holes that drain into the nasal
cavity either under or behind the middle turbinate. When these holes become
blocked from inflammation of the nasal tissues or other causes, infection of
the sinuses (sinusitis) can occur.
See a picture of
the nasal sinus cavities.
The passage that leads from the nasal
airways to the upper portion of the throat (the pharynx) connects to the
eustachian tube and the
middle ear. When the eustachian tube is blocked, fluid can build up and cause
otitis media (middle ear infection).
At
the uppermost region of the nasal cavity is the olfactory mucosa. This
specialized tissue is responsible for the sense of smell. Chemicals in the air
stimulate special nerve endings in the olfactory mucosa. These nerve endings
communicate with the brain, which interprets the signals and allows a person to
identify a certain scent. When the uppermost part of the nasal cavity is
swollen, such as from inflammation due to
allergic rhinitis or a common cold, air cannot reach
the olfactory mucosa and the person's sense of smell is reduced.
The entire nasal cavity is lined with a special lining called epithelium.
The epithelium is composed of cells with cilia, tiny hairlike projections that
move back and forth to remove particles from the nose. The epithelium is also
composed of cells that produce mucus, which keeps the nasal tissues moist. Just
below the epithelium are many nerves, arteries, and veins that allow for
sensation and supply the tissues with oxygen and nutrients. In addition, the
epithelium contains cells from the body's
immune system. These cells are able to recognize
foreign particles, such as cold viruses, so that the body can destroy them and
avoid or minimize infection.
