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Ear Pathology Online

Normal Anatomy of the Ear

Dr Sampurna Roy MD  

 

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External ear:

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 on to 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: 

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: 

Consists of :

1. Two chambers called the vestibular labyrinth and the cochlea.

2. 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.

3. 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.

 

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Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


 

 

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