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Image Link1
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Image
Link2
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Image Link3
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Image Link5
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Image Link6.
External
ear:
Image
Consists of -
1.
The auricle (pinna) is composed of
the tragus, antitragus, outer and inner helices, ear lobe and
external auditory meatus. Auricle (pinna),
is a horn-shaped structure which converges onto the external auditory meatus
(canal).
The pinna is covered by skin with the
usual range of skin adnexal structure. There is very little
subcutaneous adipose tissue except in the ear lobe.
2. The canal
is lined
by specialized skin continuous with
that of the pinna.
Ceruminous
glands, which are modified apocrine glands, are prominent and
eccrine sweat glands are not found. In the bony, inner portion of
the canal there are no adnexal structures.
Middle
ear:
Image
1. It is
separated from the external ear by the tympanic membrane. It
communicates anteriorly with the nasopharynx via auditory
(Eustachian) tube.
2. Three
tiny bones connect the ear drum to the inner ear. The bones are
called the hammer (malleus),
anvil (incus) and
stirrup (stapes).
3. The whole
of the middle ear and mastoid cavities are lined by simple squamous
or cuboidal epithelium.
4.
The middle ear normally lacks
submucosal glands but in long-standing chronic inflammation
submucosal glands lined by low cuboidal, mucus-producing cells may
develop.
Internal
ear:
Image
Consists
of -
Two
chambers called the vestibular labyrinth and the cochlea.
The vestibular labyrinth consists of elaborately formed canals (3
semicircular tubes that connect to one another), which are largely
responsible for the sense of balance.
The cochlea, which begins at the oval window, curves into a shape
that resembles a snail shell. Tiny hairs line the curves of the
cochlea. Both the labyrinth and cochlea are filled with various
fluids.
-Interconnected fluid-filled membranous labyrinth is a closed system but an extension of it, the endolymphatic duct, connects with endolymphatic sac lying in the
subdural space of the underlying brain.
-
Membranous labyrinth is lined by a simple epithelium except in the endolymphatic sac where the cells are columnar.
| Animated
Image Link:
(www.raisingdeafkids.org)
(a) Outer ear (b) ear canal
(c) eardrum
(d) hammer, anvil and stirrup (e) cochlea (f) auditory nerve |
The mastoid air
cells are composed of lamellar bone covered by periosteum over which
there is cuboidal or simple squamous epithelium. The Eustachian tube
is lined by pseudostratified ciliated columnar epithelium like that
of the upper respiratory tract.
Goblet cells
constitute about one-fifth of the epithelial cells. This proportion
increases in conditions of chronic inflammation. There is often a
diffuse scatter of lymphocytes in the submucosa of the tube, but
lymphoid follicles indicate an inflammatory process.
The most common aural disorders, in descending order of frequency,
are:
1. Acute and
chronic otitis (most often involving the middle ear and mastoid),
sometimes leading to a
Cholesteatoma ; 2. Symptomatic
Otosclerosis
; 3.
Aural Polyps
; 4.
Labyrinthitis ; 5. Carcinomas,
largely of the external ear ; and 6.
Paraganglioma - in the middle ear.
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