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Embryology and Anatomy of Ear

Question
61 out of 70
 

At birth the following structures are of adult size ex- cept:



A Tympanic cavity
B Mastoid process

C Malleus
D Tympanic ring

Ans. B Mastoid process

"Mastoid antrum is an air-filled sinus within the petrous part of temporal bone. It commincates with the middle ear by way of the aditus and has mastoid air cells arising from its walls. The antrum, but not the air cells is well developed at birth"

"Development of the mastoid air cell system does not occur until after birth, with about 90% of air cell formation being completed by the age of six with the remaining 70% taking place up to age of 78"

Hence, mastoid antrum which is not complete without its air cells, development is not complete at birth.

'The mastoid process is not present at birth and starts developing at the end of the first year and reaches its adult size at puberty."

"In infancy, the mastoid process being absent, the facial nerve emerges lateral to the tympanic portion from the stylo mastoid foramen and is likely to get injured by the usual postaural incision."

Note

f both mastoid antrum and mastoid process are given as options in any MeQ-always mark mastoid tip, as mastoid tip is a better option because mastoid antrum per se is formed at birth but its air cells are not formed whereas whole of mastoid tip/mastoid process is not present at birth.

Embryology and Anatomy of Ear Flashcard List

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