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The following CBME core competencies are covered in this chapter.
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Anatomy of the Middle Ear
Chapter Overview
The middle ear is a fascinating, air-filled chamber within the temporal bone, acting as a crucial bridge for sound transmission to the inner ear. Understanding its intricate anatomy is paramount for both MBBS and ENT PG students, as it forms the basis for diagnosing and managing a wide array of otological conditions. This comprehensive chapter, aligned with the CBME curriculum, offers a detailed yet student-friendly exploration of middle ear anatomy, ideal for university theory exams, viva questions, practical exams, and NEET PG MCQs.
Learning Objectives
After studying this chapter, the student will be able to:
- Define the middle ear and its boundaries using the six-walled box concept
- Describe the three main compartments of the tympanic cavity and their clinical significance
- Identify the ossicles, muscles, and nerves within the middle ear
- Explain the functional anatomy of the middle ear, including impedance matching and the acoustic reflex
- Discuss the anatomy of the mastoid antrum, air cell system, and their clinical relevance
- Correlate anatomical structures with common surgical approaches and complications

Introduction to the Middle Ear Cleft
Definition and Location
The middle ear, also known as the tympanic cavity, is an irregular, air-filled space in the petrous part of the temporal bone. A thin mucous membrane lines this cavity. It lies medial to the tympanic membrane and lateral to the inner ear.
The Middle Ear Cleft
Importantly, the middle ear does not exist in isolation. It forms part of a larger interconnected system called the middle ear cleft. This cleft comprises the following structures from anterior to posterior:
- The Eustachian tube (anteriorly) – Connects the middle ear to the nasopharynx
- The tympanic cavity – The middle ear proper
- The attic (epitympanum) – The superior compartment
- The aditus ad antrum – The communication between attic and mastoid antrum
- The mastoid antrum – The largest air space in the mastoid
- The mastoid air cells (posteriorly) – The largest air space in the mastoid
Key Structures Within the Tympanic Cavity
Within the tympanic cavity are several important structures:
- Ossicles – malleus, incus, stapes
- Muscles – tensor tympani and stapedius
- Nerves – chorda tympani and tympanic plexus

Functions of the Middle Ear
The middle ear serves three primary functions:
- Sound conduction and impedance matching: Transmits vibrations from the tympanic membrane to the inner ear via the ossicular chain. The ossicles provide a lever ratio of approximately 1.3:1 and a hydraulic (area) ratio of approximately 17:1 (due to the size difference between the tympanic membrane and the oval window). Together, these provide a total gain of approximately 30 dB, overcoming the impedance mismatch between air and cochlear fluid.
- Protection of the inner ear: Via the acoustic reflex (primarily stapedius muscle contraction) in response to loud sounds (approximately 70–100 dB SPL).
- Ventilation and pressure equalisation: Via the auditory (pharyngotympanic) tube, which connects the middle ear to the nasopharynx.
Middle Ear at a Glance
| Feature | Key Point |
| Location | Petrous temporal bone |
| Type | Air-filled cavity lined by mucosa |
| Main function | Sound transmission (TM → ossicles → oval window) |
| Connected system | Middle ear cleft |
| Key clinical importance | Pathway for the spread of infection to the mastoid and the brain |

Diagram Showing Divisions of the Middle Ear (Compartment-wise)
Compartmental Divisions of the Middle Ear
The middle ear is traditionally divided into three parts: the epitympanum (upper compartment), the mesotympanum (middle compartment) and the hypotympanum (lower compartment).
- Epitympanum or the Attic – This is the upper compartment. It lies above the level of pars tensa and malleolar folds but medial to the pars flaccida and the bony lateral attic wall. It is separated from the mesotympanum and hypotympanum by a series of mucosal membranes and folds.
- Mesotympanum or the tympanic cavity – This is the middle compartment, directly opposite the pars tensa of the tympanic membrane.
- Hypotympanum – This is the lower compartment, located below the level of the pars tensa and the tympanic sulcus.
Additional important areas: Beyond these main divisions, we also recognise specific anterior and posterior areas:
- Protympanum: This area lies in the anterior wall of the tympanic cavity, close to the opening of the Eustachian tube.
- Retrotympanum: This area occupies the posterior wall of the tympanic cavity.

Diagram Showing Retrotympanum and Protympanum Area
Boundaries of the Middle Ear: The Six-Walled Box Concept
The middle ear can be visualised as a six-sided box having:
- Roof
- Floor
- Anterior wall
- Posterior wall
- Lateral wall
- Medial wall
This is one of the most important frameworks for understanding middle ear anatomy.

Diagram Showing Boundaries of the Middle Ear (Six-Walled Box Concept)
Roof (Tegmental Wall)
Structure: The roof of the middle ear, also known as the tegmental wall, is a thin bony plate called the tegmen tympani. This structure forms part of the petrous portion of the temporal bone.
Relations: The tegmen tympani separates the middle ear cavity from the middle cranial fossa, which contains the temporal lobe of the brain.
Extension: The tegmen tympani extends posteriorly to form the roof of the aditus ad antrum and the mastoid antrum (tegmen antri), providing continuity to the mastoid air cells.
Cog: The cog is a small bony crest that projects inferiorly from the roof (tegmen tympani) of the epitympanum and lies anterior to the head of the malleus. It serves as an important surgical landmark by separating the anterior and posterior epitympanic spaces. Surgeons meticulously inspect the anterior epitympanic space during cholesteatoma surgery (e.g., canal wall-up procedures) to ensure complete disease removal.
Clinical Significance: Because the tegmen tympani is thin, chronic middle ear disease, especially cholesteatoma, may erode it, leading to severe intracranial complications like extradural abscess, meningitis, or temporal lobe abscess.
Floor (Jugular Wall)
Structure: The floor of the middle ear, also called the jugular wall, is also a thin bony plate.
Relations: It separates the hypotympanum from the underlying jugular fossa, which contains the dome of the internal jugular vein (jugular bulb).
Variations: Occasionally, the floor may have a congenital dehiscence (a bony deficiency), allowing the jugular bulb to project directly into the middle ear, separated only by fibrous tissue and mucous membrane. This makes the jugular bulb vulnerable to injury during surgery.
Jacobson’s Nerve: Jacobson’s nerve (the tympanic branch of the glossopharyngeal nerve, CN IX) enters the middle ear through the inferior tympanic canaliculus in the floor of the middle ear. It contributes to the tympanic plexus on the promontory and carries sensory, parasympathetic, and visceral afferent fibres. Surgeons must remember its presence when elevating the tympanomeatal flap inferiorly.
Anterior Wall (Carotid Wall)
Structure: The anterior wall, or carotid wall, is a wafer-thin bony plate (up to 3mm thin), separating the middle ear cavity from the pulsating internal carotid artery.
Openings: It features two important openings:
- Eustachian tube opening: A larger, lower opening for the entry of the Eustachian tube into the middle ear.
- Canal for Tensor Tympani: A smaller, upper opening for the canal housing the tensor tympani muscle.
Chorda Tympani: The anterior wall is also related to the anterior canaliculus (canal of Huguier), located at the junction of the anterior and medial walls of the middle ear near the petrotympanic fissure. The chorda tympani nerve exits the middle ear through this canaliculus and enters the infratemporal fossa via the petrotympanic fissure.
Pathway: Middle ear → Anterior canaliculus (Canal of Huguier) → Petrotympanic fissure → Infratemporal fossa.
Posterior Wall (Mastoid Wall)
The posterior wall, or mastoid wall, is not entirely complete.
- Inferiorly: Its lower part forms a bony partition between the middle ear and the mastoid air cells.
- Superiorly: The epitympanum (attic) continues posteriorly into the aditus ad antrum, which then connects directly to the mastoid antrum.
Aditus ad Antrum: The aditus ad antrum is the opening that connects the epitympanum (attic) with the mastoid antrum. It is the only physiological communication between the middle ear cavity and the mastoid air cell system. It is bounded laterally by the body of the incus and medially by the prominence of the lateral semicircular canal. Obstruction of the aditus by oedema or cholesteatoma can impair mastoid ventilation and predispose to mastoid disease.
Pyramid: A small bony elevation called the pyramid projects from this wall. The stapedius muscle’s tendon emerges from the apex of the pyramid and attaches to the neck of the stapes. The aditus lies superior to the pyramid.
Facial Nerve: The facial nerve (CN VII) has two segments related to the posterior and medial walls:
- Tympanic (horizontal) segment: Runs along the medial wall, superior to the oval window
- Mastoid (vertical) segment: Descends vertically in the posterior wall, just behind the pyramid
The bony canal (fallopian canal) may be dehiscent, most commonly in the tympanic segment just superior to the oval window.
Facial Recess (Posterior Sinus): This is a crucial surgical depression in the posterior wall, lateral to the pyramid.
Boundaries: It is bounded medially by the vertical part of the facial nerve, laterally by the chorda tympani nerve, and superiorly by the fossa incudis.
Surgical Importance: The facial recess approach (posterior tympanotomy) involves drilling through the facial recess in the posterior bony canal wall to gain access to the middle ear. This approach preserves the tympanic membrane, ossicular chain, and posterior canal wall, making it ideal for procedures such as cochlear implantation and mastoid surgery.
Diagram Showing Relations of the Facial Recess and Sinus Tympani
Lateral Wall (Membranous Wall)
The lateral wall primarily comprises three parts:
- Superiorly (Scutum): The scutum, a thin, sharp, wedge-shaped bony spur that forms the lateral wall of the epitympanum (attic). It is the most common site of bony erosion in acquired (pars flaccida) cholesteatoma because of its close relationship to the pars flaccida and chronic pressure exerted by the expanding cholesteatoma. Scutum erosion is a characteristic HRCT finding in attic cholesteatoma and is often one of the earliest radiological signs of the disease.
- Centrally (Tympanic membrane): This semi-transparent structure acts as a “window” into the middle ear. Through a normal tympanic membrane, you can sometimes visualise parts of the long process of incus, incudostapedial joint, round window niche, and the opening of the Eustachian tube.
- Inferiorly: The bony lateral wall of the hypotympanum.
Medial Wall (Labyrinthine Wall)
The medial wall, or labyrinthine wall, separates the middle ear from the delicate inner ear (labyrinth).
Promontory: A prominent, rounded bulge dominating the central portion of the medial wall, produced by the basal coil of the cochlea.
Tympanic Plexus: The tympanic plexus, a network of nerves, lies on the promontory. It receives contributions from the tympanic branch of the glossopharyngeal nerve (CN IX) and sympathetic fibres from the internal carotid plexus. The tympanic plexus innervates the mucous membrane of the middle ear, mastoid, and Eustachian tube.
Windows: Two crucial openings connect the middle ear to the inner ear:
- Oval Window (Fenestra Vestibuli): This kidney-shaped opening lies superior and posterior to the promontory. The footplate of the stapes is attached to it by the annular ligament, transmitting vibrations to the cochlea.
- Round Window (Fenestra Cochleae): This round opening lies inferior and posterior to the promontory, covered by the secondary tympanic membrane.
Facial Nerve Canal: The bony canal for the facial nerve lies superior to the oval window. The bony covering of the facial nerve canal is congenitally dehiscent in approximately 30-68% of individuals, most commonly in the tympanic segment (just above the oval window). This makes the nerve highly vulnerable to injury during middle ear surgery or the spread of infection.
Lateral Semicircular Canal: Above the facial nerve canal, a broader bony prominence indicates the underlying lateral semicircular canal of the inner ear.
Processus Cochleariformis: Just anterior to the oval window, the medial wall presents a hook-like projection called the processus cochleariformis. The tendon of the tensor tympani muscle takes a sharp turn here before attaching to the malleus. The processus cochleariformis is a reliable surgical landmark for the anterior end of the tympanic (horizontal) segment of the facial nerve, which lies just superior and posterior to it. Damaging this structure during surgery risks facial nerve injury.
Sinus Tympani: This complex depression lies on the medial wall in the posterior part of the middle ear. The sinus tympani is bounded: medially by the posterior semicircular canal; laterally by the facial nerve and pyramidal eminence; superiorly by the ponticulus (bony ridge between the pyramidal eminence and promontory); inferiorly by the subiculum (bony ridge between the round window niche and the styloid eminence).
Clinical Significance: The sinus tympani is a common site for cholesteatoma remnants due to its deep and hidden nature.

Contents of the Middle Ear
The tympanic cavity contains:
- Ossicles (malleus, incus, stapes)
- Muscles (Stapedius, Tensor tympani)
- Nerves (Chorda tympani, Tympanic plexus)
1. Ear Ossicles.
There are three ossicles in the middle ear – the malleus, incus and stapes. The ossicles form a semi-rigid osseous chain across the middle ear from the tympanic membrane to the oval window of the internal ear. The malleus is the most lateral ossicle, and it is attached to the tympanic membrane, whereas the stapes ossicle is attached to the oval window. The ossicles conduct sound energy from the tympanic membrane to the oval window. Muscles related to the auditory ossicles modulate movement during the transmission of vibrations from the tympanic membrane.
Malleus (hammer): The malleus is the largest ossicle. It measures 8-9 mm in length. Parts of the malleus include the head of the malleus, neck of the malleus, anterior and lateral processes, and handle of the malleus(manubrium).
- Head: The head of the malleus is the rounded upper part of the malleus, which lies in the attic region. It is suspended by the superior ligament, which runs upwards to the tegmen tympani. Its saddle-shaped posterior surface articulates with the body of the incus by a synovial joint.
- Neck: Inferior to the head of the malleus is the constricted neck of the malleus, which also lies in the attic region. The chorda tympani and tendon of the tensor tympani lie below the neck of the malleus; hence, amputation of the head of the malleus by cutting through the neck leaves both chorda tympani and tensor tympani intact.
- Anterior process: Below the neck of the malleus, there are the anterior and lateral processes. The anterior process is attached to the anterior wall of the middle ear by a ligament.
- Lateral process: The lateral process forms a knob-like projection on the outer surface of the tympanic membrane is attached to the anterior and posterior malleolar folds of the tympanic membrane.
- Handle of malleus: Below the anterior and lateral processes is the handle of the malleus, which is embedded in the fibrous layer of the tympanic membrane. The tendon of the tensor tympani muscle inserts on the medial surface of the handle. Chorda tympani crosses the handle of the malleus just above the insertion of the tensor tympani muscle.
Incus (Anvil). It is the second bone in the series of ear ossicles. Parts of the incus include the body of the incus and the long and short process.
- Body. It articulates with the head of the malleus and lies in the attic. It is suspended by the superior incudal ligament coming from the tegmen tympani.
- Short process. The short process projects backwards to lie in the fossa incudis. A short suspensory ligament attaches it to the upper posterior wall of the middle ear.
- Long process. It hangs vertically downward into the mesotympanum almost parallel to the handle of the malleus. The tip of the incus, also known as the lenticular process, articulates with the head of the stapes and forms the incudostapedial joint.
Stapes (stirrup): The stapes is the third and smallest bone in the ossicular chain. The stapes measures approximately 2.5–3.5 mm in height (crura to footplate) and 3 mm in width across the footplate. It is attached to the oval window by the annular ligament. Parts of the stapes include the head, neck, anterior and posterior crura and footplate.


2. Muscles of the Middle Ear
There are two muscles:
- Stapedius
- Tensor tympani
Stapedius muscle. The stapedius arises from the apex of the pyramid, which is a small projection on the posterior (mastoid) wall of the middle ear and passes forward to attach to the posterior surface of the neck of the stapes. In response to loud sounds (approximately 70–100 dB SPL, which is roughly 85–95 dB above normal hearing threshold for most individuals), the stapedius muscle contracts, pulling the stapes posteriorly, thereby dampening the sound and preventing noise trauma to the inner ear (acoustic reflex). Stapedius is a second arch muscle and is supplied by the nerve to stapedius, which is a branch of CN VII.
Tensor tympani muscle. This is a long, slender muscle arising from the bony canal present on the anterior wall of the middle ear. It is present above the opening of the eustachian tube. Its tendon turns through a right angle around the processus cochleariformis and passes laterally and inserts into the medial aspect of the upper end of the handle of the malleus. It tenses the tympanic membrane. Contraction of the tensor tympani pulls the handle of the malleus medially. Tensor tympani tenses the tympanic membrane and reduces its mobility. Although it may contribute to attenuation of loud sounds, the stapedius is the principal muscle responsible for the acoustic reflex. The muscle develops from the first arch and is supplied by the medial pterygoid branch of the mandibular nerve (V3).

Diagram Showing Muscles Associated with the Ossicles
3. Nerves of the Middle Ear
There are two nerves:
- Chorda Tympani
- Tympanic Plexus
Chorda Tympani Nerve. It is a branch of the facial nerve.
Course: It enters the middle ear through the posterior canaliculus at the junction of the lateral and posterior walls of the middle ear. It runs on the medial surface of the tympanic membrane between its mucosal and fibrous layers. On the malleus, it runs medially just below the neck of the malleus and above the attachment of the tendon of the tensor tympani. It further continues forward and leaves the middle ear through the anterior canaliculus.
Functions: It carries taste sensation from the anterior two-thirds of the tongue and supplies secretomotor fibres to the submandibular and sublingual salivary glands.
Tympanic Plexus. The tympanic plexus lies on the promontory and is formed by the
- Tympanic branch of the glossopharyngeal and
- Caroticotympanic nerves (sympathetic fibres) from the plexus around the internal carotid artery.
The tympanic plexus innervates the medial surface of the tympanic membrane, tympanic cavity, mastoid air cells and the bony eustachian tube.
The tympanic plexus also gives off a major branch (the lesser petrosal nerve), which supplies preganglionic parasympathetic fibres to the otic ganglion. The tympanic branch of the glossopharyngeal nerve carries secretomotor fibres for the parotid gland.
Clinical Relevance: Sectioning of the tympanic branch of the glossopharyngeal nerve can be carried out in the middle ear in cases of Frey’s syndrome.
Course of secretomotor fibres to the parotid:
Inferior salivary nucleus → CN IX → Tympanic branch → Tympanic plexus → Lesser petrosal nerve → Otic ganglion → Auriculotemporal nerve → Parotid gland.

Diagram Showing Tympanic Plexus
Middle Ear Cleft: Mastoid Antrum and Air Cell System
The mastoid is an integral part of the middle ear cleft, serving as a reservoir for air and a common site for ear infections to spread.

Diagram Showing Mastoid Antrum and its Air Cell System
1. Mastoid Antrum
The mastoid antrum is a relatively large, air-containing space located in the upper part of the mastoid process.
Dimensions: Approximately 10 mm in height, 10–12 mm in width, and 15–17 mm in depth (anteroposteriorly) in adults.
Volume: Varies significantly; average volume ranges from 0.5 to 2 ml, depending on the degree of pneumatisation.
Development: Unlike the mastoid air cells, the antrum is well-developed at birth.
Communication: Directly communicates with the epitympanum via the aditus ad antrum.
Mucosal Continuity: The mucous membrane lining the mastoid air cells is continuous with the mucous membrane of the entire middle ear cleft. Consequently, infections in the middle ear can easily spread to the mastoid.

Boundaries of the Mastoid Antrum
Boundaries of Mastoid Antrum
- Roof: It is formed by a thin layer of bone called the tegmen antri, which separates the mastoid antrum from the middle cranial fossa, where the brain’s temporal lobe resides. If an infection in the middle ear cleft breaches this thin wall, it can travel to the brain. This can result in serious complications such as extradural abscess, meningitis and temporal lobe abscess.
- Lateral wall: The lateral wall of the antrum is formed by a plate of bone, which is on average 1.5 cm thick in the adult. It is marked externally on the surface of the mastoid by the suprameatal (MacEwen’s) triangle.
- Medial wall: It is formed by the petrous bone and related to the posterior semicircular canal, endolymphatic sac, and dura of the posterior cranial fossa.
- Anterior: Anteriorly, the mastoid antrum communicates with the attic through the aditus ad antrum.
- Posterior wall: It is primarily formed by the mastoid bone and has an important role in connecting the middle ear to the mastoid air cells. The posterior wall separates the mastoid antrum from the sigmoid sinus, a major venous channel that drains blood from the brain. If an infection in the middle ear cleft spreads and breaches the posterior wall, it can extend to the sigmoid sinus. This can lead to a severe condition known as sigmoid sinus thrombophlebitis. In this condition, the drainage of blood from the central nervous system becomes impaired, and infection may spread further into the cerebellum or the brainstem, leading to life-threatening issues.
- Floor: It is formed by the mastoid bone and communicates with the mastoid air cells.
2. MacEwen’s Triangle (Suprameatal Triangle)
MacEwen’s triangle is an important external landmark for the mastoid antrum. You can define its boundaries:
- Superiorly: The linea temporalis (temporal line), a ridge of bone extending posteriorly from the zygomatic process, which marks the lower border of the temporalis muscle and approximates the floor of the middle cranial fossa.
- Anteriorly: The posterosuperior margin of the external auditory canal (EAC).
- Posteriorly: A tangent to the posterior margin of the EAC.

Boundaries of Macewen’s triangle
3. Pneumatization of the Mastoid Air Cell System
The mastoid process itself contains a “honeycomb” of air cells beneath its bony cortex. The extent of this pneumatization varies significantly among individuals.
Types of Mastoid Pneumatization:
- Well-pneumatized (Cellular): Characterised by well-developed air cells with thin intervening bony septa. This is the most common type.
- Diploetic: Contains marrow spaces and only a few scattered air cells.
- Sclerotic (Acellular): Lacks both air cells and marrow spaces, appearing as dense bone. This type is often associated with chronic mastoid infections.
Regardless of the pneumatization type, the mastoid antrum is always present. In sclerotic mastoids, the antrum is usually small, and the sigmoid sinus may be anteposed (positioned more anteriorly), increasing surgical risk. Abscesses can form in relation to these air cells, sometimes far from the main mastoid region.

4. Classification of Mastoid Air Cells by Location
Mastoid air cells are named based on their anatomical location:
- Zygomatic cells are present in the root of zygoma.
- Tegmen cells are present in the tegmen tympani.
- Perisinus cells are present in the the sinus plate.
- Retrofacial cells are present around the facial nerve.
- Perilabyrinthine cells are present above, below and behind the labyrinth.
- Peritubal are present around the eustachian tube.
- Tip cells are present medial and lateral to the digastric ridge in the tip of mastoid.
- Marginal cells are present behind the sinus plate and may extend into the occipital bone.
- Squamosal cells are present in the squamous part of temporal bones.
5. Korner’s Septum (Petrosquamosal Suture)
The squamous and petrous parts of the temporal bone together form the mastoid.
Description: In some individuals, the petrosquamosal suture persists as a distinct bony plate known as Korner’s septum. This septum separates superficial squamosal cells from deeper petrosal cells.
Surgical Importance: Korner’s septum causes difficulty in locating the antrum and the deeper cells. Korner’s septum must be identified and often removed to ensure complete exenteration of deeper petrosal air cells and prevent residual disease. Failure to remove Korner’s septum may lead to incomplete disease removal and recurrence.

Diagram Showing Korner’s Septum
Middle Ear Cleft Mucosa
General Features: The middle ear mucosa is essentially mucus-secreting respiratory mucosa bearing cilia on its surface. Mucosa of the nasopharynx is continuous with that of the middle ear cleft. The mucosa wraps ossicles, muscles, ligaments and nerves in a similar way as peritoneum wraps various viscera in the abdomen, raising several mucosal folds and dividing the middle ear into various compartments. So, all the middle ear structures lie outside the mucous membrane. The middle ear contains nothing but air; all the structures lie outside the mucous membrane. The mucous membrane of the nasopharynx is continuous with that of the middle ear cleft.
Histological Variation: Histologically, the eustachian tube is lined by ciliated epithelium, which is pseudostratified columnar in the cartilaginous part, columnar in the bony part, with several mucous glands in the submucosa. The tympanic cavity is lined by ciliated columnar epithelium in its anterior and inferior part, which changes to cuboidal type in the posterior part. Epitympanum and mastoid air cells are lined by flat, non-ciliated epithelium.
Compartments and Folds of the Middle Ear
Ossicles and their mucosal folds separate mesotympanum from epitympanum (attic).
| 1. | Compartments of Epitympanum | a. Prussak’s space: Its boundaries, which limit the spread of infection to other compartments, are following: – Lateral: Pars flaccida – Medial: Neck of malleus – Floor: Lateral process of malleus – Roof: Lateral malleolar fold, which contains the superior malleolar ligament |
| b. Attic compartments: Cog divides the attic into two compartments – a smaller anterior epitympanum and a larger posterior epitympanum. The space between the lateral malleolar fold and the lateral incudal fold provides communication with Prussak’s space. | ||
| 2. | Compartments of Mesotympanum | Inferior incudal space: Its boundaries are following – Superior: Lateral incudal fold – Medial: Medial incudal fold – Lateral: Posterior malleolar fold – Anterior: Interossicular fold |
| Anterior pouch of von Troeltsch: It lies between the following boundaries: – Medial: Anterior malleolar fold – Lateral: Portion of the tympanic membrane anterior to the handle of malleus |
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| Posterior pouch of von Troeltsch: It is situated between the following boundaries: – Medial: Posterior malleolar fold – Lateral: Portion of the tympanic membrane posterior to the handle of malleus. |
Blood Supply of Middle Ear
The middle ear is supplied by eight arteries, out of which two are the main, i.e.
- Anterior tympanic branch of maxillary artery, which supplies the tympanic membrane, malleus, incus and anterior part of tympanic cavity.
- Stylomastoid branch of the posterior auricular artery, which supplies the stapedius muscle and the posterior part of tympanic cavity.
Six minor vessels are:
- Mastoid branch of stylomastoid artery, which supplies mastoid air cells.
- Petrosal branch of middle meningeal artery (runs along greater petrosal nerve), which supplies the roof of mastoid and epitympanum.
- Superior tympanic branch of middle meningeal artery, which supplies the canal for tensor tympani muscle, malleus and incus.
- Inferior tympanic branch of ascending pharyngeal artery, which supplies the mesotympanum.
- Branch of artery of pterygoid canal (runs along eustachian tube), which supplies the mesotympanum and hypotympanum
- Caroticotympanic arteries (from the internal carotid artery), which supply the mesotympanum and hypotympanum
| Branch | Parent artery | Region supplied |
| Anterior tympanic | Maxillary artery | Tympanic membrane Malleus and incus Anterior part of tympanic cavity |
| Stylomastoid | Posterior auricular | Posterior part of tympanic cavity Stapedius muscle |
| Mastoid | Stylomastoid | Mastoid air cells |
| Petrosal | Middle meningeal | Roof of mastoid Roof of epitympanum |
| Superior tympanic | Middle meningeal | Malleus and incus Tensor tympani |
| Inferior tympanic | Ascending pharyngeal | Mesotympanum |
| Branch from artery | Artery of pterygoid canal | Meso- and hypotympanum |
| Caroticotympanic arteries | Internal carotid | Meso- and hypotympanum |
Veins drain into pterygoid venous plexus and superior petrosal sinus.
Lymphatic Drainage of the Middle Ear
The lymphatics of the middle ear drain into the retropharyngeal and parotid nodes. Eustachian tube lymphatics drain into the retropharyngeal group of lymph nodes. The internal ear has no lymphatics.
Anatomy of the Auditory Tube.
Click on the link: https://www.entlecture.com/eustachian-tube-anatomy/
———— End of the chapter ————
High-Yield Points for NEET PG and University Exams
- The middle ear is part of the middle ear cleft, extending from the auditory tube to the mastoid air cells
- The middle ear is divided into five compartments: epitympanum, mesotympanum, hypotympanum, protympanum, and retrotympanum
- The tegmen tympani separates the middle ear from the temporal lobe and is a route for intracranial spread of infection
- The jugular bulb lies beneath the floor (jugular wall) and may be dehiscent
- The carotid wall separates the middle ear from the internal carotid artery and contains openings for the auditory tube and tensor tympani
- The posterior wall contains the pyramid, facial nerve canal, and facial recess, and leads to the mastoid via the aditus
- Scutum erosion is typical of attic cholesteatoma
- The medial wall contains the promontory, oval window, round window, facial nerve canal, and lateral semicircular canal bulge
- The sinus tympani is a common site for cholesteatoma remnants
- Ossicles transmit sound: TM → malleus → incus → stapes → oval window
- Stapedius is supplied by CN VII; tensor tympani by V3
- The chorda tympani carries taste from the anterior two-thirds of the tongue and crosses the handle of the malleus
- The tympanic plexus gives rise to the lesser petrosal nerve → otic ganglion → parotid secretomotor pathway
- The mastoid antrum is present at birth and communicates with the attic via the aditus ad antrum
- Korner’s septum may cause an incomplete mastoidectomy
MCQs
- Q1. A 10-year-old boy presents with a 2-month history of ear discharge and hearing loss. HRCT temporal bone reveals scutum erosion and a soft tissue mass in the attic. Which compartment is most likely involved? A. Hypotympanum B. Epitympanum C. Mesotympanum D. Protympanum
- Q2. During middle ear surgery for cholesteatoma, a surgeon carefully inspects the anterior epitympanum. What structure divides the attic into anterior and posterior compartments? A. Promontory B. Ponticulus C. Cog D. Processus cochleariformis
- Q3. A child presents with congenital dehiscence of the floor of the middle ear, exposing the jugular bulb. Which wall of middle ear is deficient? A. Roof (tegmental wall) B. Floor (jugular wall) C. Anterior wall (carotid wall) D. Medial wall (labyrinthine wall)
- Q4. The nerve that enters through the floor of the middle ear is: A. Chorda tympani B. Facial nerve C. Jacobson’s nerve D. Lesser petrosal nerve
- Q5. A cochlear implant surgeon accesses the middle ear through facial recess approach. The facial recess is bounded: A. Laterally by facial nerve, medially by chorda tympani B. Medially by facial nerve, laterally by chorda tympani C. Superiorly by oval window, inferiorly by pyramid D. Superiorly by eustachian tube, inferiorly by promontory
- Q6. A patient has taste disturbances and dry mouth following middle ear surgery. The likely injured structure is: A. Jacobson’s nerve B. Lesser petrosal nerve C. Chorda tympani nerve D. Greater petrosal nerve
- Q7. The stapedius muscle originates from which bony projection of the posterior wall? A. Pyramid B. Ponticulus C. Subiculum D. Fossa incudis
- Q8. In a child with recurrent acute otitis media, infection can spread directly to the brain due to thin bone separating middle ear from cranial cavity. This bone is called: A. Tegmen tympani B. Scutum C. Promontory D. Processus cochleariformis
- Q9. In a HRCT scan of the mastoid, a large, well-developed mastoid antrum is seen communicating with attic via: A. Sinus tympani B. Aditus ad antrum C. Facial recess D. Round window niche
- Q10. Which of the following is the smallest ossicle? A. Malleus B. Incus C. Stapes D. Lenticular process
Answers : 1: B. 2: C. 3: B. 4: C. 5: B. 6: C. 7: A. 8: A. 9: B. 10: C.
Clinical Case Scenarios (Practical + Viva Oriented)
1. Case 1: A 14-year-old boy presents with foul-smelling ear discharge and attic retraction pocket. Otoscopy shows scutum erosion. Most likely diagnosis: Attic cholesteatoma. Most likely site involved: Epitympanum (attic). Key surgical concern: Residual disease in sinus tympani and anterior epitympanic space.
2. Case 2: A 35-year-old patient undergoing tympanoplasty develops postoperative altered taste sensation. Most likely nerve injured: Chorda tympani. Function affected: Taste from the anterior two-thirds of the tongue.
3. Case 3: A patient with chronic otitis media develops facial weakness. HRCT shows a bony canal defect. Most likely explanation: Dehiscent fallopian canal with facial nerve exposure. Most vulnerable site: Tympanic segment of the facial nerve, just superior to the oval window (the most common site of dehiscence).
4. Case 4: During middle ear surgery, profuse bleeding occurs from the floor of the middle ear. Most likely structure injured: High jugular bulb. Reason: Congenital dehiscence of the jugular wall.
FAQ in Viva
- Why is the tegmen tympani clinically important? It is thin, and infection can spread to the brain, causing meningitis or an abscess.
- What is the scutum? The scutum is the bony lateral wall of the attic, commonly eroded in cholesteatoma.
- What is Prussak’s space? It is a small epitympanic space bounded by the pars flaccida and the malleus neck and is important in cholesteatoma spread.
- What is sinus tympani? It is a deep recess in the posterior medial wall and is a common site for residual cholesteatoma.
- Which nerve carries taste through the middle ear? Chorda tympani carries taste from the anterior two-thirds of the tongue.
- Which muscle protects against loud sounds? Stapedius contracts during loud sounds and reduces stapes movement.
———— End ————
Download full PDF Link:
Anatomy of Middle Ear Walls Best Lecture Notes Dr Rahul Bagla ENT Textbook
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Anatomy of Ear Best PPT Notes Lectures Dr Rahul Bagla ENT Textbook
Reference Textbooks.
- Scott-Brown, Textbook of Otorhinolaryngology-Head and Neck Surgery.
- Glasscock-Shambaugh, Textbook of Surgery of the Ear.
- P L Dhingra, Textbook of Diseases of Ear, Nose and Throat.
- Hazarika P, Textbook of Ear Nose Throat And Head Neck Surgery Clinical Practical.
- Mohan Bansal, Textbook of Diseases of Ear, Nose and Throat Head and Neck Surgery
- Hans Behrbohm, Textbook of Ear, Nose, and Throat Diseases With Head and Neck Surgery.
- Salah Mansour, Middle Ear Diseases – Advances in Diagnosis and Management.
- Logan Turner, Textbook of Diseases of The Nose, Throat and Ear Head And Neck Surgery.
- Rob and smith, Textbook of Operative surgery.
- Anirban Biswas, Textbook of Clinical Audio-vestibulometry.
- Arnold, U. Ganzer, Textbook of Otorhinolaryngology, Head and Neck Surgery.
Author:

Dr. Rahul Bagla
MBBS (MAMC, Delhi) MS ENT (UCMS, Delhi)
Fellow Rhinoplasty & Facial Plastic Surgery.
Renowned Teaching Faculty
Mail: msrahulbagla@gmail.com
India
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- Please read. Anatomy of External Ear. https://www.entlecture.com/anatomy-of-ear/
- Please read. Anatomy of Temporal Bone. https://www.entlecture.com/anatomy-of-temporal-bone/
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thanks for nice informatios
Thanks for reading.
This is an amazing review of middle ear anatomy. Very well illustrated. Thank you so much and stay blessed Sir.
Thanks
This information about the middle ear is correct and well presented
Thanks
Thank you
Thanks for reading.
Very well written and summarised..
Contains all the details of this topic.
Thanks
Middle ear anatomy – Simple, Clear. I can’t believe this is free!
It’s now my go-to reference before ward rounds. I am doing post-graduation at University of Buenos Aires, Argentina. My colleagues also read your book. Your book is quite famous here. Make a PDF book.
Thanks
I’m delighted to hear this, Dr Gonzalez. It means a lot that you and your colleagues at the University of Buenos Aires find the content simple and clear. In fact, I’m already working on a PDF edition.
Regards
Dr Rahul Bagla
Great explaination sir
Thank you so much, Dr Negi! I’m glad the explanation resonated with you.
Regards
Dr Rahul Bagla
Amazing
Excellent book with clear explanations, schematic diagrams as well as real time pictures orients us in a right way for both PG entrance and University exams.
Also the clinical cases are very helpful for clinical postings and practical exams.
Excellent book with clear explanations, schematic diagrams as well as real time pictures orients us in a right way for both PG entrance and University exams.
Also the clinical cases are very helpful for clinical postings and practical exams.
This book is excellent for beginners. The language is very simple and easy to understand. It covers all the main Ear, Nose, and Throat topics clearly. The points are short, which makes it perfect for quick study. Highly recommended!
I always found middle ear difficult to understand..like for real…but these notes makes it too easy to understand and learn….
Thank you so much Sir for this valuable guide..