Malleus

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Overview of the structures of the middle ear.

The malleus is one of three tiny interconnected bones in the middle ear cavity (tympanic cavity) which are collectively called the auditory ossicles. From lateral to medial these are the malleus, incus and stapes. The word 'malleus' is Latin for 'hammer' and is so called due to its mallet shape.

The malleus is the largest of the three ossicles and measures about 8cm in length. It is related laterally to the tympanic membrane and articulates medially with the body of the incus forming a synovial joint. It consist of five main parts which include: head of malleus , neck of malleus, anterior process, lateral process, and handle of malleus.

The head of malleus refers to the upper rounded part that sits in the epitympanic recess of the tympanic cavity. It bears a cartilaginous articular facet on its medial surface for articulation with the incus. The head of
malleus is connected to the roof of the epitympanic recess by the superior ligament of malleus and to the posterior border of the tympanic notch, a small defect in the posterior edge of the tympanic ring, by the lateral ligament of malleus.

Below the head is a constriction that forms the neck of the malleus. The neck is crossed on its medial surface by chorda tympani nerve, a branch of the facial nerve (CN VII) that runs through the middle ear on its way to supply taste to the anterior two thirds of the tongue.

Situated below the neck of malleus are the anterior and lateral processes of malleus. The anterior process projects forwards and is fixed to the anterior wall of the tympanic cavity by anterior ligament of malleus. The conical-shaped lateral process, on the other hand, projects laterally and attaches to the anterior and posterior malleolar folds in the upper part of the tympanic membrane.

The malleus extends further inferiorly from the anterior and lateral processes as the handle of malleus. The internal surface of the tympanic membrane is attached to the lateral aspect of the handle of malleus, which follows the movements of the tympanic membrane. The upper part of the handle also serves as an insertion point for the tensor tympani muscle which upon contraction tenses the tympanic membrane by pulling on the handle of malleus medially.