Mastoid antrum

MASTOID ANTRUM

Q. 1

Mac Ewan’s triangle is the landmark for:

 A

Maxillary sinus

 B

Mastoid antrum

 C

Frontal sinus

 D

None

Q. 1

Mac Ewan’s triangle is the landmark for:

 A

Maxillary sinus

 B

Mastoid antrum

 C

Frontal sinus

 D

None

Ans. B

Explanation:

Q. 2

The suprameatal triangle overlies:

 A

Mastoid antrum

 B

Mastoid air cells

 C

Antrum

 D

Facial nerve

Q. 2

The suprameatal triangle overlies:

 A

Mastoid antrum

 B

Mastoid air cells

 C

Antrum

 D

Facial nerve

Ans. A

Explanation:

Q. 3

Anatomical landmark indicating position of mastoid antrum:

 A

Suprameatal triangle

 B

Spine of Henle

 C

Tip of the mastoid process

 D

None

Q. 3

Anatomical landmark indicating position of mastoid antrum:

 A

Suprameatal triangle

 B

Spine of Henle

 C

Tip of the mastoid process

 D

None

Ans. A

Explanation:

Q. 4

All of the follwoing are of the size of adult at birth expect? 

 A

Tympanic membrane

 B

Ossicle

 C

Tympanic cavity

 D

Mastoid

Q. 4

All of the follwoing are of the size of adult at birth expect? 

 A

Tympanic membrane

 B

Ossicle

 C

Tympanic cavity

 D

Mastoid

Ans. D

Explanation:

 

 

Development of the mastoid air cell system does not occur until afterbirth, with about 90% of air cell formation being completed by the age of six with the remaining 10% taking place up to age of 18

 



Q. 5

Which of the following is not a pneumatic bone?

 A

Ethmoid

 B

Sphenoid

 C

Maxillary

 D

Mastoid

Q. 5

Which of the following is not a pneumatic bone?

 A

Ethmoid

 B

Sphenoid

 C

Maxillary

 D

Mastoid

Ans. D

Explanation:

Q. 6

Which of the following forms lateral wall of mastoid antrum?      

 A

Mastoid process

 B

Suprameatal triangle

 C

Petrous temporal bone

 D

Tympanic cleft

Q. 6

Which of the following forms lateral wall of mastoid antrum?      

 A

Mastoid process

 B

Suprameatal triangle

 C

Petrous temporal bone

 D

Tympanic cleft

Ans. B

Explanation:

The lateral wall of the mastoid antrum is formed by a plate of bone which is on average 1.5 dm thick in the adult. It is marked externally on the surface of mastoid by suprameatal/ MacEwen’s triangle

Mastoid antrum/ Tympanic antrum/ Antrum mastoideum/ Valsalva’s antrum

It is a cavity in the petrous portion of the temporal bone, communicating posteriorly with the mastoid cells and anteriorly with the epitympanic recess of the middle ear via the aditus to mastoid antrum (entrance to the mastoid antrum).

  • In the temporal bone, between the posterior wall of the external acoustic meatus and the posterior root of the zygomatic process is the area called the suprameatal triangle, mastoid fossa, foveola suprameatica, or Macewen’s triangle, through which an instrument may be pushed into the mastoid antrum.
  • In the adult, the antrum lies approximately 1.5 to 2 cm deep to the suprameatal triangle.
  • This is an important landmark when performing a cortical mastoidectomy.

Q. 7

Shortest skull diameter:  

March 2013

 A

Biparietal

 B

Mentovertical

 C

Bitemporal

 D

Bimastoid

Q. 7

Shortest skull diameter:  

March 2013

 A

Biparietal

 B

Mentovertical

 C

Bitemporal

 D

Bimastoid

Ans. D

Explanation:

Ans. D i.e. Bimastoid

Fetal skull

  • Shortest diameter of fetal skull: Bimastoid (7.5 cm)
  • Largest diameter of fetal skull: Mentovertical (14 cm)

Q. 8

Mastoid antrum is present in which part of temporal bone‑

 A

Tympanic

 B

Petrous

 C

Squamous

 D

Mostoid

Q. 8

Mastoid antrum is present in which part of temporal bone‑

 A

Tympanic

 B

Petrous

 C

Squamous

 D

Mostoid

Ans. B

Explanation:

Mastoid

  • It is an air sinus in the petrous temporal bone.
  • Its upper anterior wall has the opening of aditus, while medial wall is related to posterior semicircular canal (SCC).
  • Posteriorly lies the sigmoid sinus.
  • The posterior belly of digastric muscle forms a groove in the base of mastoid bone.
  • The corresponding ridge inside the mastoid lies lateral not only to sigmoid sinus but also to facial nerve and is a useful landmark.
  • The roof is formed by tegmen antri separating it from middle cranial fossa and temporal lobe of brain. o Anteroinferior is the descending part of facial nerve canal (or fallopian canal).
  • Lateral wall is formed by squamous temporal bone and is easily palpable behind the pinna.


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