The Middle Ear

The Middle Ear

The middle ear is the middle part of the ear which is lined with mucous membrane and lies in the petrous part of the temporal bone. The middle ear consists of
-Tympanic membrane
-Middle ear cavity
-Ossicles
-Eustachian tube.

1.      Tympanic membrane
Tympanic membrane, is a thin, cone-shaped membrane that separates the external ear from the middle ear.It is 9-10mm tall, 8-9 mm wide and 0.1 mm thick.

It is anatomically separated into four quadrants:
·         Anterosuperior quadrant
·         Anteroinferior quadrant
·         Posteroinferior quadrant
·         Posterosuperior quadrant

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Tympanic membrane can be divided into two parts:

(a) Pars Tensa

It forms most of tympanic membrane. Its periphery is thickened to form a fibrocartilaginous ring called the annulus tympanicus . Thecentral part of pars tensa is tented inwards at the level of the tip of malleus and is called the umbo. A bright cone of light can be seen radiating from the tip of malleus to the periphery in the anteroinferior quadrant.

(b) Pars Flaccida (Shrapnel's Membrane)

This is situated above the lateral process of malleus . It is not so taut and may appear slightly pinkish.

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Layers of Tympanic Membrane

Tympanic membrane consists of three layers:

(i) Outer epithelial layer, which is continuous with the skin lining the meatus.
(ii) Inner mucosal layer, which is continuous with the mucosa of the middle ear.
(iii) Middle fibrous layer, which encloses the handle of malleus and has three types of fibres-the radial, circular and the parabolic.

2.      Eustachian Tube

eustachian-tube-picture.jpg     images (1).jpg
The Eustachian tube also auditory tube orpharyngotympanic tube, is a tube that links the nasopharynx to the middle ear. It is a part of the middle ear. In adult humans the Eustachian tube is approximately 37 mm long. 
E.T is in a collapsed state so that individual voice and breathing sounds are not directly transmitted to the ear. E.T is open on;y under stressof air pressure changes or by the action of pharyngeal muscles during swallowing or yawning.
The tube is bony in structurewhen it is adjacent to middle ear and cartilaginous when is near the nasopharynx.








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