MCQ – 66191

Identify the structures marked as A,B,C,D in the picture below? 

A.	A-Malleus. B-Incus. C-Stapes. D-Tympanic membrane.
B.	A-Malleus. B-Incus. C-Tympanic membrane. D-Stapes.
C.	A-Malleus. B-Tympanic membrane. C-Stapes. D-Incus.
D.	A-Stapes. B-Incus. C-Malleus. D-Tympanic membrane.

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Correct Answer � A Explanation

Ans;A.)

A-Malleus.

B-Incus.

C-Stapes.

D-Tympanic membrane.

Middle ear Ossicles

MALLEUS

• This bone is shaped like a hammer hence the name.
• This is the largest of the three ossicles of the middle ear cavity.
• It has a head, neck and three processes arising from below the neck.
• The overall length of the malleus ranges between 7.5 – 9 mm..
• Below the neck the bone broadens and gives rise to the following:
• the anterior process from which a slender anterior ligament arises to insert into the petrotympanic fissure;
• the lateral process which receives the anterior and posterior malleolar folds from the annulus tympanicum, and
• the handle which runs downwards, medially and slightly backwards between the mucous and fibrous layers of the centre of tympanic membrane.
• Cone of light is due to Handle of malleus.

INCUS

• This bone is shaped like an anvil.
• It articulates with the malleus and has a body and two processes.
• The body lies in the epitympanum and has a cartilage covered articular facet corresponding to that of the malleus.
• The short process projects backwards from the body to lie in the fossa incudis. It is infact attached to the fossa incudis by a short ligament.
• The long process of the incus descends into the mesotympanum behind and medial to the handle of the malleus.
• At its tip there is a small medially directed lenticular process which articulates with the stapes.

STAPES

• The stapes consists of a head, neck, two crura and a base (footplate).
• The head of the stapes points laterally and has a small cartilage covered depression for articulation with the lenticular process of the incus.
• The neck of the stapes gives rise to two crura which join the foot plate closing the oval window
• The average dimensions of the foot plate is 3mm x 1.4mm.