Middle ear Ossicles
- 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.
- 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.
- 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.