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Embryology and Anatomy of Ear

Question
42 out of 70
 

True about Eustachian tube: (LQ)



A Length is 36 mm in adults and 1.6 to 3 mm in children

B Higher elastin content in adults

C Ventilatory function of ear better developed in infants

D More horizontal in adults

E Angulated in infants

Ans. B Higher elastin content in adults Ref. Dhingra 6th/ed p57

"Eustachian tube serves to ventilate the middle ear and exchange nasopharyngeal air in the middle ear. In children, ET is relatively narrow.

It is prone to obstruction" when mucosa swell in response to infection or allergic challenge and it results in middle ear effusion"

Eustachian Tube

It connects nasopharynx with the tympanic cavity. In adult, it is about 36 cm long and runs downward, forward medially from its tympanic end, forming an angle of 450 with the horizontal.

The tympanic end of the tube is body and is situated in the anterior wall of middle ear. A little above the level of floor. The pharyngeal end of the tube is slit like and is situated in the lateral wall of the nasopharynx, 1-1.25 cm behind the posterior end of inferior tubinate.?

It develops from first arch and partly from second arch.

Table (Dhingra 5te, p 65): Differences between infant and adult Eustachian tube

Length

Infant

13-18 cm birth (about half as long as in adult)

Adult

36 mm (31-38 mm)

Direction

Angulation at isthmus

Bony versus cartilaginous

Tubal cartilaginous part

Density of elastin at the hinge

Ostmann's pad of fat

More horizontal? At birth it forms an angle of 100

with the horizontal At age 7 and later it is 450

No angulation

Bony parts is slightly longer than 1/3 of the total

length of the tube and is relatively wider

Flaccid. Retrograde reflux nasopharyngeal

Less dense; tube does not efficiently close by recoil

Less in volume

Forms an angle of 450 with the horizonal

Angulation persent

Bony part 1/3; cartilagious part 32/3

Comparatively rigid, Remains closed and protects

Density of elastin more and helps to keep the tune closed by recoil of cartilage

Large and helps to keep the tube closed

Embryology and Anatomy of Ear Flashcard List

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