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EAR AND ITS DISEASES





Category: Diseases of The Eye and Ear

The external ear is called auricle or pinna. It is an oval funnel-shaped
organ. The canal leading in to the membrane (drum) is called the external
auditory meatus. It extends inward about one and one-quarter inches and
terminates in a membrane.

Membrane Tympani (drum) which separates the external ear from the tympanic
cavity. To examine the drum, you must pull the ear backward and outward to
make the canal straight.

Membrane Tympani (the drum) Membrane This is situated at the inner end
of the canal and separates it from the tympanum or middle ear. It is
placed like the membrane in the telephone. It is pearly gray in color.
This membrane not only serves as a protection to the delicate structures
within the tympanum, but also receives the sound vibrations from without
and transmits them to the ossicular (bony) chain of the middle ear.

The Tympanum or Middle Ear. This cavity just beyond the drum, which forms
the greater part of its outer wall, is an irregular cavity, compressed
from without inward and situated in the petrous bone. The mastoid cells
lie behind. It is filled with air and communicates with the nose-pharynx
(naso-pharynx) by the eustachian tube. The upper portion of this cavity,
the attic, lies immediately below the middle lobe of the brain, separated
from it by a thin layer of bone, which forms the roof of the cavity. This
cavity is separated from the internal ear.



The Eustachian tube. This is the channel through which the middle ear
communicates with the pharynx. With an opening in the anterior of the
middle ear, a bony canal passes from this point, inward, forward, and
downward through the petrous bone, when it merges into a cartilaginous
canal, which terminates in a funnel-shaped protuberance, with a slit-like
orifice, located in the nose pharynx. This is the eustachian tube. It is
lined with mucous membrane like the throat. The air goes up from the
throat, through this canal to the middle ear. The mucous membrane of the
middle ear is continuous with that of the nose-pharynx through the
eustachian tube. So you can readily understand how easy it is for an
inflammation of the throat to extend to the middle ear through the
eustachian tube.

The posterior wall which has the greatest height, reveals in its upper
portion a passage (antrum) through which the vault of the tympanum (attic)
communicates with the cells of the mastoid process, situated posteriorly.
From this description you see how near to each other these parts are
placed and when one becomes diseased the disease can extend to the other
part or parts. The brain is separated from some of these cavities by a
very thin shell of bone, and the disease can soon affect the brain through
infection or breaking through the thin structures that separates the
parts.

Diseases of the middle ear and the mastoid are always to be considered
serious, and should be very closely watched. A child with a running ear is
in danger, for it may at any time become closed up and serious.





Next: ECZEMA OF THE EXTERNAL EAR (Auricle)

Previous: SQUINT OR STRABISMUS



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