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Otoscope structure

- May 22, 2018 -

The eardrum is approximately 2.5 cm to 3.5 cm from the external auditory canal and is located between the external auditory canal and the tympanum. The eardrum height is about 9 mm and the width is about 8 mm. The average area is about 90 mm2 and the thickness is 0.1 mm. The eardrum is elliptical and its shape is like a funnel. It is placed obliquely in the external auditory canal and is 45 to 50 with the external auditory canal. Causes the outer wall of the external auditory canal to be shorter than the frontal wall. In infants and young children, because the external auditory canal bone is not developed and the eardrum is almost parallel to the bottom wall of the external auditory meatus, it is difficult to see when inspecting the eardrum. The adult eardrum has a length of about 9 mm, a width of about 8 mm, and a thickness of 0.1 mm.

Although the eardrum is thin, it has three layers of anatomy:

1 The epithelium is continuous with the skin of the external auditory canal.

2 The middle layer is composed of radial and circular cilia, so there is a certain degree of elasticity and tension. It is a fibrous layer (radial on the outside and round on the inside). There is a small part above the eardrum. There is no intermediate fibrous layer. It is relatively thin and loose. It is called the relaxed part, and part of the eardrum with the fibrous layer is called the tension part. Hammer shank attached to the middle of the fiber layer.

3 The inner layer is a mucous layer, which is continuous with the tympanic mucosa.

After perforation of the eardrum, the outer epithelial layer and the inner layer of mucous membranes can be regenerated, and the middle layer has no regeneration ability. Loose parts of the eardrum lack a middle layer.Laparoscopic Surgery Instruments

The shank of the malleolus is attached to the eardrum from top to bottom, above the center of the eardrum, so that the eardrum is pulled inward to make it funnel-shaped, much like the speaker of a radio. Its central depression is called the umbilicus of the eardrum. Slightly forward to the upper edge of the Ministry of tension there is a gray-white dot-like small protrusions, called the hammer convex, that is, the short segment of the malleus lifts up the eardrum, clinically known as short-bump. Hammer bulge is caused by the shortening of the malleus and the eardrum. On the surface of the eardrum, there is a white stripe from the front to the back of the umbilicus and the hammer and the hamstring is formed in the eardrum and called the hammer. The end of the warp is exactly in the center of the eardrum, called the umbilicus. Underneath the umbilicus, a triangular retroreflective region, called the cone of light, is directed from the umbilicus to the eardrum. The cone of light is caused by the reflection of light projected onto the eardrum. When the shape of the eardrum changes, the shape and position of the cone of light often changes.

There is a fold (bi) before and on the side of the hammer, the former being called the front and the latter being called the back. On top of this ridge, the eardrum is loosened and the loose part is called a direct attachment to the sacrum scale. Underneath it is a strained part, which is embedded in the ear ditch of the ear bone by a drum ring.Laparoscopic Instruments

For the purpose of clinical records, the eardrum is often divided into four quadrants, ie, an imaginary straight line along the handle of the malleolus, and the eardrum is divided into an upper, anterior, and posterior line by perpendicularly intersecting the eardrum. And after the next four quadrant areas.

Blood supply to eardrum

The supply of the deep ear arteries of the maxillary artery, and branches of the anterior and posterior tympanic arteries are mainly distributed in the sag, the malleolus, and the peripheries of the eardrum. The superficial jugular veins flow outward and the medial veins of the eardrum flow to the transverse sinus and dura mater veins and partly to the eustachian tube veins.

Nerve of eardrum

The outer half of the eardrum is distributed by the vagus nerve and the first half comes from the frontal branch of the trigeminal nerve. The medial side of the eardrum is dominated by the tympanic branch of the glossopharyngeal nerve, so pain in the ear and pharynx often affects each other. The distribution of nerves is similar to that of blood vessels. Fibers are concentrated in the regions of slack and malleolus, whereas the nerves in the nervous regions are poorly distributed. Therefore, in the absence of local or general anesthesia, incisions in the posterior portion of the normal eardrum do not cause excessive pain.



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