Anterior Wall Of Mesotympanum :

1.Internal Carotid Artery Bulge

2.Bulge of the Semicanal of the Tensor tympani muscle.

3.Orifice of the Eustachian tube is immediately inferior to this bulge.

4.Canal Of Hugier : Exit for Chordatympani nerve.

Posterior Wall :

-It Lies Close to the Mastoid Air Cells.

*The key anatomic features are :-Pyramidal Eminence : Bony Projection through which the Tendon of the Stapedius Muscle Arises.

-Laterally, Chordal Eminence houses the Iter Chordae Posterius by which the Chorda Tympani nerve enters the Tympanic Cavity.

Medial Wall :(the Surgical “Floor” of the middle ear) features three depressions: the Sinus tympani, Oval window niche, and Round window niche.

-The Sinus Tympani is defined by the ponticulus Superiorly, the subiculum Inferiorly, the mastoid segment of the facial nerve Laterally, and the posterior semicircular canal Medially.- There is substantial variability in theposterior extension (surgical “depth”) of the Sinus tympani, ranging from “shallow” to “deep.” -The Oval Window niche, occupied by the stapes footplate, is located anterosuperior to the ponticulus.

-The Round Window niche can be found posteroinferior to the Promontory,the bulge created by the Basal turn of the Cochlea.

Prussak`s Space :-It is the superior recess of the tympanic membrane.

-Medially : Head & Neck of Malleus-AnteroSuperiorly : Lateral Malleal Ligament-Inferiorly : Anterior and Posterior Malleal Folds-Laterally : Shrapnell`s Membrane

Clinical significance :-Prusaks space is important because it is a site for Parsflaccida acquired Cholesteatoma.-A Cholesteatoma forms when there is a deep retraction pocket in the tympanic membrane. The lining of the tympanic membrane, which is skin, is usually shed.But if the membrane is retracted it gets trapped.The debris collects and enlarges and ultimately forms a Cholesteatoma, or Cholesterol Granule.

-This Cholesteatoma,in turn,can erode the middle ear ossicles,facial nerve,inner ear and even involve the brain.

OSSICLES :

MALLEUS :Head(Caput), Manubrium (Handle),Neck,Anterior & Lateral Process.

-Lateral Process has a Cartilaginous Cap that merges with Pars Propria Of T.M.- Plica Mallearis- L.P & Umbo

Incus :

-Largest of all the thee Ossicles.-Has a Body and 3 processes : Long, Short & Lenticular Process.-The Body Of Incus Articulates with the Head of Malleus in the Epitympanum.-The Short process of Incus is Anchored in the Incudal fossa by the Posterior Incudal Ligament.-The Lenticular process, at the terminus of the Long process,articulates with the stapes.

-The Long process of the Incus, perhaps owing to its tenuous blood supply,is particularly prone to osteitic resorption in the face of chronic otitis media.

STAPES :

-The stapes is the smallest and most medial of the ossicles. -Its Head articulates with the lenticular process of the incus.-Footplate sits in the oval window,surrounded by the StapedioVestibular Ligament.-The Arch of the stapes, composed of an Anterior and Posterior Crus, links the Head and the Footplate.

Middle Ear Muscles1.Tensor tympani muscle :-Origin : from the walls of its semicanal, greater wing of the sphenoid, and cartilage of the eustachian tube. -The Tendon of the tensor tympani muscle sweeps around the Cochleariform Process and across the tympanic cavity to attach to the medial aspect of the neck and Handle of the malleus.-Innervation : Trigeminal Nerve.

The facial nerve is seen in its vertical and tympanic segments. Anterosuperiorly,the facial nerve passes superior to the tensortympani tendon.

2.STAPEDIUS :*Origin  :-From the internal walls of the Pyramidal eminence  in the Post.Wall  of tympanic cavity of the ear.

*Course :-The stapedius muscle runs in a vertical sulcus in the posterior wall of the tympanic cavity adjacent to the facial nerve.

*Insertion : Poterior Crus, Or occasionally to the head or Neck of the stapes. *Innervation : Facial Nerve.*Action : Draws the Head Of the Stapes Backwards.

Pneumatization :

-The extent of pneumatization of the temporal bonevaries according to Heredity, Environment, Nutrition,Infection, and Eustachian tube function.

-There are five recognized regions of pneumatization:

1. Middle Ear 2. Mastoid 3. PeriLabyrinthine 4. Petrous Apex 5. Accessory

Eustachian Tube :

-The Eustachian Tube extends approximately 36 mm from the Anterior aspect of the Tympanic Cavity to the Posterior aspect of the Nasopharynx.

-Functions : ventilate, clear, and protect the middle ear.

- The lining Mucosa of the tube has an abundanceof Mucociliary Cells, important to its clearance function.

-The Antero-Medial 2/3 of the Eustachian tube isFibro-cartilaginous(24mm), whereas the remainder 1/3 is Bony(12mm)