Hearing - Middle Ear Development

From Embryology
Embryology - 19 Jun 2024    Facebook link Pinterest link Twitter link  Expand to Translate  
Google Translate - select your language from the list shown below (this will open a new external page)

العربية | català | 中文 | 中國傳統的 | français | Deutsche | עִברִית | हिंदी | bahasa Indonesia | italiano | 日本語 | 한국어 | မြန်မာ | Pilipino | Polskie | português | ਪੰਜਾਬੀ ਦੇ | Română | русский | Español | Swahili | Svensk | ไทย | Türkçe | اردو | ייִדיש | Tiếng Việt    These external translations are automated and may not be accurate. (More? About Translations)


Adult hearing embryonic origins
Adult hearing embryonic origins.

The embryology of the middle ear requires many separate components from different embryonic origins. The tympanic membrane separates the outer ear from the middle ear and is formed initially from the first pharyngeal arch membrane. The middle ear bones (ossicles) are derived from separate origins in the first and second arch mesenchyme. The space in which these bones sit (tympanic cavity) is derived from the first pharyngeal pouch and is connected directly to the oral cavity by a hollow tube (auditory tube). In addition there are two muscles (tensor tympani and stapedius) formed from arch mesenchyme. (More? pharyngeal arch, bone, muscle).

Note that in other species, such as the guinea pig, the malleus and incus are normally found as a single complex.

Hearing Links: Introduction | inner ear | middle ear | outer ear | balance | placode | hearing neural | Science Lecture | Lecture Movie | Medicine Lecture | Stage 22 | hearing abnormalities | hearing test | sensory | Student project

  Categories: Hearing | Outer Ear | Middle Ear | Inner Ear | Balance

Historic Embryology - Hearing 
Historic Embryology: 1880 Platypus cochlea | 1892 Vertebrate Ear | 1902 Development of Hearing | 1906 Membranous Labyrinth | 1910 Auditory Nerve | 1913 Tectorial Membrane | 1918 Human Embryo Otic Capsule | 1918 Cochlea | 1918 Grays Anatomy | 1922 Human Auricle | 1922 Otic Primordia | 1931 Internal Ear Scalae | 1932 Otic Capsule 1 | 1933 Otic Capsule 2 | 1936 Otic Capsule 3 | 1933 Endolymphatic Sac | 1934 Otic Vesicle | 1934 Membranous Labyrinth | 1934 External Ear | 1938 Stapes - 7 to 21 weeks | 1938 Stapes - Term to Adult | 1940 Stapes | 1942 Stapes - Embryo 6.7 to 50 mm | 1943 Stapes - Fetus 75 to 150 mm | 1946 Aquaductus cochleae and periotic (perilymphatic) duct | 1946 aquaeductus cochleae | 1948 Fissula ante fenestram | 1948 Stapes - Fetus 160 mm to term | 1959 Auditory Ossicles | 1963 Human Otocyst | Historic Disclaimer

Some Recent Findings

  • Developmental Disruptions of the Human Stapes[1] "Twenty-five temporal bone specimens from 18 patients with congenital stapes malformations were identified in the Mass Eye and Ear temporal bone collection. Serial sections stained with hematoxylin and eosin were examined by light microscopy and the morphology of the stapes was compared to age-matched controls. Each case of stapes malformation could be classified into one of four malformation types based on our current understanding of the embryologic origin of the subunits of the stapes and timing of development. Twenty-seven percent of stapes malformations had a Type I morphology characterized by a hypoplastic or absent inner footplate and hypoplastic to absent mesoderm footplate or oval window. The crura and capitulum may be absent, monopodal or dysmorphic. Eleven percent expressed a Type II malformation with dysmorphic or monopodal capitulum and crura and a fixed footplate. Twenty-seven percent were of Type III with a dysmorphic or monopodal capitulum and or crura. The footplate, and thereby oval window is present and without fixation. The most common malformation, Type IV, was isolated footplate fixation observed in 33% of cases."
  • Single origin of the epithelium of the human middle ear[2] "The epithelium lining the human middle ear and adjacent temporal bone cavity shows a varying morphological appearance throughout these cavities. Its embryologic origin has long been debated and recently got attention in a newly proposed theory of a dual embryologic origin. The epithelial morphology and its differentiating capabilities are of significance in future mucosa-targeted therapeutic agents and could affect surgical approaches of the temporal bone. This study aims to analyze reported murine histological findings that led to the theory of a dual epithelial embryological origin and immunohistochemically investigate whether such an epithelial embryological origin in the human fetal middle ear could be true. By combining a sagittal sectioning technique and immuno-histochemical staining, a comprehensive immuno-histological overview of the fetal human middle ear during a critical stage of tympanic cavitation was provided. A critical analysis of previously reported findings leading to the theory of a dual epithelial embryological origin and a comparison of these findings to the findings in the human fetal middle ear was performed. The reported findings and critical analysis provide multiple arguments for an entirely endodermal embryonic origin of the epithelium lining the tympanic cavity. Different morphological epithelial appearances throughout the tympanic and temporal bone cavities could be explained by different stages of epithelial differentiation rather than different embryologic origin and endodermal rupture does not seem to be a necessity for these cavities to form."
  • Region-specific endodermal signals direct neural crest cells to form the three middle ear ossicles[3] "Defects in the middle ear ossicles - malleus, incus and stapes - can lead to conductive hearing loss. During development, neural crest cells (NCCs) migrate from the dorsal hindbrain to specific locations in pharyngeal arch (PA) 1 and 2, to form the malleus-incus and stapes, respectively. It is unclear how migratory NCCs reach their proper destination in the PA and initiate mesenchymal condensation to form specific ossicles. We show that secreted molecules sonic hedgehog (SHH) and bone morphogenetic protein 4 (BMP4) emanating from the pharyngeal endoderm are important in instructing region-specific NCC condensation to form malleus-incus and stapes, respectively, in mouse. Tissue-specific knockout of Shh in the pharyngeal endoderm or Smo (a transducer of SHH signaling) in NCCs causes the loss of malleus-incus condensation in PA1 but only affects the maintenance of stapes condensation in PA2. By contrast, knockout of Bmp4 in the pharyngeal endoderm or Smad4 (a transducer of TGFβ/BMP signaling) in the NCCs disrupts NCC migration into the stapes region in PA2, affecting stapes formation. These results indicate that region-specific endodermal signals direct formation of specific middle ear ossicles." Development
  • Reporting and Description for Congenital Middle Ear Malformations to Facilitate Surgical Management[4] "The aim of this work was to report and describe the different types of congenital middle ear malformations in order to guide surgical treatment approaches and improve outcomes for affected patients. The authors reviewed patients with congenital middle ear malformations who received surgical treatment between September 2010 and March 2017. Patient characteristics, middle ear deformities, and surgical procedures were documented. RESULTS: In this retrospective study, 35 patients were reviewed. A description of middle ear malformation was proposed that considers ear embryogenesis and focuses on stapes deformity, with the main purpose of facilitating surgical approach selection to reconstruct the ossicular chain. Patients were classified into 3 categories: type I (19 cases), mobile stapes footplate, which included type Ia with normal stapes suprastructure and type Ib with abnormal stapes suprastructure; type II (4 cases), fixed stapes footplate, which included type IIa with normal ossicular chain and type IIb with abnormal ossicular chain; and type III (12 cases), oval window bony atresia or aplasia, with or without round window atresia. Types II and III could have concomitant aberrant facial nerve. Different surgical approaches are described."
  • Development of the Human Incus[5] "We examined histological sections of 55 human embryos and fetuses at 6 to 13 weeks of development. At 6 weeks of development (16 Carnegie Stage), the incus anlage was found at the cranial end of the first pharyngeal arch. At this stage, each of the three anlagen of the ossicles in the middle ear were independent in different locations. At Carnegie Stage 17 a homogeneous interzone clearly defined the incus and malleus anlagen. The cranial end of the incus was located very close to the otic capsule. At 7 and 8 weeks was characterized by the short limb of the incus connecting with the otic capsule. At 9 weeks was characterized by an initial disconnection of the incus from the otic capsule. At 13 weeks, a cavity appeared between the otic capsule and incus. Our results provide significant evidence that the human incus developed from the first pharyngeal arch but independently from Meckel's cartilage." incus
More recent papers  
Mark Hill.jpg
PubMed logo.gif

This table allows an automated computer search of the external PubMed database using the listed "Search term" text link.

  • This search now requires a manual link as the original PubMed extension has been disabled.
  • The displayed list of references do not reflect any editorial selection of material based on content or relevance.
  • References also appear on this list based upon the date of the actual page viewing.

References listed on the rest of the content page and the associated discussion page (listed under the publication year sub-headings) do include some editorial selection based upon both relevance and availability.

More? References | Discussion Page | Journal Searches | 2019 References | 2020 References

Search term: Middle Ear Development | Stapes Development | Malleus Development | Incus Development | Tensor Tympani Development | Stapedius Development

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • A new developmental mechanism for the separation of the mammalian middle ear ossicles from the jaw[6]"Multiple mammalian lineages independently evolved a definitive mammalian middle ear (DMME) through breakdown of Meckel's cartilage (MC). However, the cellular and molecular drivers of this evolutionary transition remain unknown for most mammal groups. Here, we identify such drivers in the living marsupial opossum Monodelphis domestica, whose MC transformation during development anatomically mirrors the evolutionary transformation observed in fossils. Specifically, we link increases in cellular apoptosis and TGF-BR2 signalling to MC breakdown in opossums. We demonstrate that a simple change in TGF-β signalling is sufficient to inhibit MC breakdown during opossum development, indicating that changes in TGF-β signalling might be key during mammalian evolution." TGF-beta
  • Early development of the malleus and incus in humans[7] "It is widely accepted by developmental biologists that the malleus and incus of the mammalian middle ear are first pharyngeal arch derivatives, a contention based originally on classical embryology that has now been backed up by molecular evidence from rodent models. However, it has been claimed in several studies of human ossicular development that the manubrium of the malleus and long process of the incus are actually derived from the second arch. This 'dual-arch' interpretation is commonly presented in otolaryngology textbooks, and it has been used by clinicians to explain the aetiology of certain congenital abnormalities of the human middle ear. In order to re-examine the origins of the human malleus and incus, we made three-dimensional reconstructions of the pharyngeal region of human embryos from 7 to 28 mm crown-rump length, based on serial histological sections from the Boyd Collection. ...We therefore conclude that the histological evidence, on balance, favours the 'classical' notion that the human malleus and incus are first-arch structures. The embryological basis of congenital ossicular abnormalities should be reconsidered in this light."
  • Fetal development of the elastic-fiber-mediated enthesis in the human middle ear[8] "In the human middle ear, the annular ligament of the incudostapedial joint and the insertions of the tensor tympani and stapedius muscles contain abundant elastic fibers; i.e., the elastic-fiber-mediated entheses. Hyaluronan also coexists with the elastic fibers. In the present study using immunohistochemistry, we demonstrated the distribution of elastin not only in the incudostapedial joint but also in the other two joints of the middle ear in adults and fetuses. In adults, the expression of elastin did not extend out of the annular ligament composed of mature elastic fibers but clearly overlapped with it. Electron microscopic observations of the annular ligament demonstrated a few microfibrils along the elastic fibers. Thus, in contrast to the vocal cord, the middle ear entheses seemed not to contain elaunin and oxytalan fibers. In mid-term fetuses (at approximately 15-16 weeks of gestation) before opening of the external acoustic meatus, the incudostapedial joint showed abundant elastic fibers, but the incudomalleolar and stapediovestibular joints did not. At this stage, hyaluronan was not colocalized, but distributed diffusely in loose mesenchymal tissues surrounding the ear ossicles. Therefore, fetal development of elastin and elastic fibers in the middle ear entheses is unlikely to require acoustic oscillation. In late-stage fetuses (25-30 weeks), whose ear ossicles were almost the same size as those in adults, we observed bundling and branching of elastic fibers. However, hyaluronan expression was not as strong as in adults. Colocalization between elastic fibers and hyaluronan appeared to be a result of postnatal maturation of the entheses."
  • Defects in middle ear cavitation cause conductive hearing loss in the Tcof1 mutant mouse[9] "Treacher Collins syndrome (TCS) is an autosomal dominant disorder of facial development that results from mutations in the gene TCOF1. CHL is a common feature of TCS but the causes of the hearing defect have not been studied. In this study, we have utilized Tcof1 mutant mice to dissect the developmental mechanisms underlying CHL. Our results demonstrate that effective cavitation of the middle ear is intimately linked to growth of the auditory bulla, the neural crest cell-derived structure that encapsulates all middle ear components, and that defects in these processes have a profoundly detrimental effect on hearing."

Middle Ear Origins

Pharyngeal arch cartilages
  • neural crest from the first and second pharyngeal arches forms the cartilage origin of the middle ear bones (ossicles).
    • first arch cartilage - (Meckel's) malleus and incus
    • second arch cartilage - (Reichart's) stapes
  • first pharyngeal pouch endoderm forms the auditory tube that enlarges to incorporate the tympanic cavity surrounding the ossicles.
    • endoderm forms the lining epithelium and glands.
  • mesoderm from the first and second arch forms the middle ear muscles
    • first arch - tensor tympani muscle
    • second arch - stapedius muscle

Middle Ear Genes - gooscoid, RARs, Prx1, Otx2, Hoxa1, Hoxb1, endothelian related molecules

Eustacian tube angle

Week 8

Cross-section of human embryo Carnegie stage 22 during Week 8.

Stage 22 image 159.jpg Stage 22 image 161.jpg

Middle ear structure visible are the primordial maleus, the developing tensor tympani muscle, the developing auditory tube (tubo tympanic recess) extending from the oral cavity towards the middle ear region. Note the ossicle is still embedded, and surrounded by, the mesenchyme of the head.


Gray0916.jpg Gray0917.jpg Gray0918.jpg
malleus (hammer)
incus (anvil)
stapes (stirrup)

Middle ear development begins closely associated with head formation and involves both the foregut tube (pharynx) and the pharyngeal arches. Pharyngeal arches form the main anatomical structures of the head and neck, including all components of the middle and outer ear. The three middle ear bones or auditory ossicles (malleus, incus, stapes) are formed from the cartilage template found within pharyngeal arch 1 and 2.

These bones are commonly named the "hammer" (malleus), "anvil" (incus) and "stirrup" (stapes), and the cartilage bands are historically named after two German anatomists and are called Meckel’s cartilage (first pharyngeal arch; named after Johann Friedrich Meckel, 1781–1833) and Reichert’s cartilage (second pharyngeal arch; named after Karl Bogislaus Reichert, 1811–1883). There are several theories as to how each arch cartilage contributes individual components of the middle ear ossicles. For example, a recent study suggests a mesenchymal origin for the stapes rather than directly from Reichert's cartilage.[10] Meckel’s cartilage first appears histologically at Carnegie stage 16 and Reichert’s cartilage slightly later.

The early stages of auditory ossicle development all occur within the solid mesenchyme of the pharyngeal arches until the eighth month of development, then within a fluid-filled space for the final month, and finally only postnatal in the neonate in the air-filled tympanic cavity. This transition in auditory ossicle environment means that the middle ear does not function correctly until after birth, and any prenatal conduction to the cochlea must be mediated through bone conduction.

During development of the tympanic cavity, the auditory ossicles are held in their correct anatomic positions by supporting ligaments. Arch cartilages ossify by the process of endochondral ossification, where a pre-existing cartilage template is first formed and later replaced by bone. Endochondral ossification is the main process of bone formation throughout the entire skeleton, except for the cranial vault and the clavicle that ossify by a process of intramembranous ossification.

Initially, the malleus and incus form as a single structure, and it is only later that they separate to form two separate bones. Ossification continues through the entire fetal period, and the newly formed bones also have a transient bone marrow cavity. The marrow cavity is still present at birth, in both the malleus and the incus, and with continued ossification is lost during the first two years after birth. Postnatally, first the malleus and then the incus lose their marrow spaces.



Malleus (left) A. From behind. B. From within.

The malleus develops from the first pharyngeal arch cartilage (Meckel's cartilage) and was named from its resemblance to a hammer.

The structure of the adult bone can be divided into a head, neck, and three processes (manubrium, anterior and lateral processes). In the fetus, of the three processes the anterior process is the longest and is in direct continuity with Meckel's cartilage.

Malleus ossification is initiated in the fetal period.[11] [12]

The newborn and infant malleus head normally contains bone marrow, that is eventually replaced by bone.[13]

Malleus Development (timing from[12])

  • 16 weeks - two cortical fascicles situated in the neck
  • 21 weeks - fascicles extend towards the head
  • 23 weeks - extend towards to the lateral process
  • 24 weeks - extend towards to the handle
  • 29 weeks - in the handle force lines are transmitted via three cardinal fascicles (two of them via the cortical fascicle and one via the centre)
  • 31 weeks - consolidated by this time
Adult Malleus Anatomy
Component Latin Description
Head capitulum mallei large upper extremity of the bone, oval in shape articulates posteriorly with the incus, being free in the rest of its extent facet for articulation with the incus is constricted near the middle (consists of an upper larger and lower smaller part nearly a right angle with each other) opposite the constriction (lower margin of the facet projects in the form of a process, cog-tooth or malleus spur)
Neck collum mallei narrow contracted part, just beneath the head below it is a prominence various processes are attached to the prominence
Handle manubrium mallei connected by its lateral margin with the tympanic membrane directed downward, medialward, and backward decreases in size toward its free end, which is curved slightly forward, and flattened transversely. Medial side, near its upper end, is a slight projection, into which the tendon of the tensor tympani is inserted
Anterior Process processus anterior (Folii), processus gracilis delicate spicule from the eminence below the neck directed forward to the petrotympanic fissure to which it is connected by ligamentous fibers
Lateral Process processus lateralis, processus brevis a slight conical projection from the root of the manubrium directed laterally, and is attached to the upper part of the tympanic membrane attached by means of the anterior and posterior malleolar folds, to the extremities of the notch of Rivinus.


A series of different abnormalities of the anterior process and manubrium mallei (malleus handle) have been described.[14]

  • thick bony bar - extending from the neck of the malleus fused with the posterior bony wall or the tympanic bone.
  • thick bony bar and a cartilaginous malleus handle - cartilage appears attached to the anterior part of the bony bar.
  • no bony bar - a V-shaped ossicle one end connected to the malleus head by fibrous tissue.

Historic Embryology

Hanson JR. and Anson BJ. Development of the malleus of the human ear; Illustrated in atlas series. (1962) Q Bull Northwest Univ Med Sch. 36(2): 119–137. PMID: 13904457.



Incus (left) A. From within. B. From the front

The incus develops from the first pharyngeal arch cartilage (Meckel's cartilage) and named from the resemblance to an anvil, onsists of a body and two crura.

The two crura diverge from one another nearly at right angles.

Gray suggested the incus has more like a "premolar tooth" appearance, with two roots, which differ in length, and are widely separated from each other.

Incus ossification is initiated in the fetal period.[11]

Incus Development (timing from[12])

  • 16 weeks - force lines start through two cortical fascicles in the long process
  • 17 to 20 weeks - two cortical fascicles progressively extend in a rostro-caudal direction
  • 21 weeks - occupy the whole extension of the long process
  • 22 weeks - fusion of both cortical fascicles begins.
  • 30 weeks - strengthened by the crossing of bone trabeculae from one cortical to another. Two fascicles come out of the incus body, surrounding the medullary cavity and going in the direction of the short process.

The newborn and infant incus body normally contains bone marrow, that is eventually replaced by bone.[13]

From recent study of histological sections from 55 human embryos and fetuses at 6 to 13 weeks of development.[5] 6 weeks

    • (Carnegie Stage 16) - incus anlage was found at the cranial end of the first pharyngeal arch. At this stage, each of the three anlagen of the ossicles in the middle ear were independent in different locations.
    • (Carnegie Stage 16) - a homogeneous interzone clearly defined the incus and malleus anlagen. The cranial end of the incus was located very close to the otic capsule.
  • 7 and 8 weeks - the short limb of the incus connecting with the otic capsule.
  • 9 weeks - an initial disconnection of the incus from the otic capsule.
  • 13 weeks - a cavity appeared between the otic capsule and incus.
Adult Incus Anatomy
Component Latin Description
Body corpus incudis somewhat cubical but compressed transversely anterior surface is a deeply concavo-convex facet facet articulates with malleus head
Short Crus crus breve (short process) somewhat conical in shape projects almost horizontally backward attached to fossa incudis, in lower and back part of epitympanic recess
Long Crus crus longum (long process) descends nearly vertically behind and parallel to manubrium of malleus bending medialward, ends in a rounded projection, the lenticular process lenticular process is tipped with cartilage, and articulates with stapes head



A. Left stapes. B. Base of stapes, medial surface.

The stapes develops mainly from the second pharyngeal arch neural crest cartilage (Reichardt's cartilage). The stapedial footplate like the nearby annular ligament and the connected otic capsule around the oval window is of mesoderm origin.[15]

Stapes Development (timing from[12])

  • 28 weeks - tympanic membrane of the stapes footplate undergoes a remodelling process with bony trabeculae deposited

The adult ossicle is by its resemblance to a stirrup, structurally consisting of a head, neck, two crura, and a base.

Adult Stapes Anatomy
Component Latin Description
Head capitulum stapedis presents a depression covered by cartilage articulates with lenticular process of incus
Neck constricted part of the bone, succeeding the head gives insertion to tendon of stapedius muscle
Two crura crus anterius and crus posterius diverge from the neck , connected at ends by a flattened oval plate anterior is shorter and less curved than the posterior
Base basis stapedis forms the foot-plate of the stirrup fixed to margin of fenestra vestibuli by a ring of ligamentous fibers

Historic Embryology

For historical development and adult anatomy of the stapes see the series of papers by Cauldwell and Anson from the 1930's to 1940's.

1938 Stapes - 7 to 21 weeks[16]

1938 Stapes - Term to Adult[17]

1940 Adult form of the human stapes in the light of its development[18]

1942 Stapes Embryo 6.7 to 50 mm[19]

1943 Stapes Fetus 75 to 150 mm[20]

1948 Stapes Fetus 160 mm to Term[21]

Tympanic Membrane

The tympanic membrane (membrana tympani) or "ear drum", separates the external acoustic meatus from the tympanic cavity. In the adult, this thin membrane is nearly oval in shape about 9 to 10 mm in diameter. The circumference is slightly thickened to form a fibrocartilaginous ring that is attached to the tympanic sulcus at the inner end of the meatus. The malleus manubrium is attached to the medial surface of the membrane and is the mechanism for transmitting vibration of the tympanic membrane to the other middle ear ossicles. See also recent review.[22]

Middle Ear Muscles

Tensor tympani development, week 8 stage 22

The middle ear also contains the two smallest muscles of the body, the stapedius and tensor tympani muscles, which both differentiate from arch mesenchyme. These muscles form and differentiate in a similar fashion to other developing skeletal muscle. Initially myoblasts proliferate under the influence of growth factors in the region of where the muscle will form. Myoblasts are the embryonic undifferentiated single cells of all skeletal muscles.

Tensor Tympani

Adult tensor tympani is classed as a mixed muscle containing slow (type 1) and fast (type 2A, and probably 2X) muscle fibers.


Adult mammalian stapedius muscle contains mainly (77%) fast oxidative glycolytic type muscle fibers and the avian muscle only contains fast fibers.

A recent study[23] of the stapedius region (see table below) and muscle development in 50 human embryos and fetuses between 38 days to 17 weeks post-conception identified 2 origins:

  1. tendon - derives from the internal segment of the interhyale
  2. belly - located in the second pharyngeal arch, medially to the facial nerve and near the interhyale

interhyale - term describing the internal part of the second pharyngeal arch that forms the tendon of the stapedius muscle

Stapedius Timeline
CRL (mm) Description
13 6 Presumptive stapedial area
14 7 Appearance of the stapedial anlage
16 9 Relationship between the stapedial artery and the stapedial anlage. Appearance of the interhyale
17 12 Delimitation of the parts of the stapedial anlage
18 16 Chondrogenesis phase. Start of involution of the stapedial artery
20 18.5 Delimitation of the ossicular anlages. Cartilaginous phase. Disappearance of the stapedial artery
22 26 Delimitation of the interhyale
23 28 Anlage of the stapedial muscle tendon
Data from Table 1[23]   Links: middle ear

Links: Musculoskeletal System - Muscle Development

Tympanic Cavity

The tympanic cavity (cavum tympani) extends from the endoderm of the first pharyngeal arch pouch to surround the middle ear ossicles. This small air-filled space is connected to the oral cavity by the narrow auditory tube. The lining epithelium has been suggested as having dual origins, but a recent study has confirmed the endodermal origin of this epithelium.[2] The adult tympanic cavity anatomy is a single space constricted slightly into an upper (attic) and a lower (atrium) chamber.

Auditory Tube

The auditory tube or eustachian tube (named after Bartolomeo Eustachi, 1500–1574) (or otopharyngeal or pharyngotympanic tube) develops from the first pharyngeal pouch and is lined with endoderm. This narrow cavity links the pharynx to the middle ear and is continuous with the tympanic cavity. The auditory tube has two main functions: ventilation, to allow the equalization of pressure in the middle ear, and clearance, to allow the middle ear fluid continuously produced by the epithelial lining to drain from the middle ear.

In normal human development, the auditory tube has an almost straight posterolateral to anteromedial pathway. The main growth of the auditory tube occurs in extension and lumen of the cartilaginous portion in the fetal period between weeks 16 to 28.

At birth, and in the young child, the tube is both shorter (8-9 mm) compared
to the adult length (17-18 mm), runs almost horizontal and is narrower in
diameter. Head growth in the child to adult size results in a longer wider tube that runs at approximately 45 degrees to the horizontal. The auditory tube is also normally closed and is opened by muscles—in the infant this is only a single muscle, the tensor palati muscle. In the adult the auditory tube is now opened by two separate muscles, the tensor palati and levator palati muscles.

The middle ear cavity or tympanic cavity is formed by an expansion of the pharynx. The initial early cavity lining is formed by the pharyngeal endoderm epithelium. The epithelium will then continue to expand, to eventually also line the entire mastoid antrum.

  • derived from first pharyngeal pouch
  • extends as tubotympanic recess - during week 5 recess contacts outer ear canal
  • mesoderm between 2 canals forms tympanic membrane
  • expands to form tympanic recess
  • stalk of recess forms auditory tube(eustachian tube, pharyngotympanic tube)

Skeletal elements surrounding the auditory tube have 2 parts:

  1. bony lateral portion - arises from the anterior wall of the auditory bulla.
  2. cartilage portion - covers the dorsal region along the length of the tube.

Mouse models have shown that the cartilage is mostly mesoderm in origin with a small part formed also from neural crest.


The auditory tube is surrounded by four muscles, two are attached to the muscles insert into the palate and key in opening the tube:

  1. tensor veli palatini - first pharyngeal arch
  2. levator veli palatini - fourth pharyngeal arch

Auditory Tube Postnatal Changes

Eustacian tube angle.jpg


  • longer (34-36 mm)
  • wider
  • runs at approximately 45 degrees to the horizontal
  • opened by two separate muscles (tensor palati and levator palati)


  • shorter (17-18 mm)
  • narrower
  • runs almost horizontal
  • opened by a single muscle (tensor palati muscle)

Adult Middle Ear

The adult middle ear, like the inner ear, eventually will lie within the petrous portion of temporal bone. Initially, both the middle and inner ear form within mesenchyme, embryonic connective tissue, forming the otic capsule, and this will also form the base of the skull. The mesenchyme differentiates first to form cartilage, forming a structure known as the chondrocranium. This initial cartilage is gradually replaced by bone forming at a number of sites within the cartilage, ossification centers. The initial bone that is formed also contains marrow spaces that disappear with ongoing ossification (Yokoyama et al., 1999). Between the weeks 16 to 24, centers of ossification appear in the remaining cartilage of the otic capsule, and these continue to ossify to eventually form mastoid process of temporal bone.

Other Species

Avian - the columella is a single ossicle, it has a shaft and footplate inserted into the oval window.

Additional Images


Historic Disclaimer - information about historic embryology pages 
Mark Hill.jpg
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Keith A. Human Embryology and Morphology. (1902) London: Edward Arnold.

Frazer JE. The early formations of the middle ear and eustachian tube - a criticism. (1922) J Anat. 57(1): 18-30. PMID 17103958


  1. Elias TGA & Santos F. (2022). Developmental Disruptions of the Human Stapes. Otol Neurotol , 43, e461-e466. PMID: 35120079 DOI.
  2. 2.0 2.1 van Waegeningh HF, Ebbens FA, van Spronsen E & Oostra RJ. (2019). Single origin of the epithelium of the human middle ear. Mech. Dev. , , 103556. PMID: 31121244 DOI.
  3. Ankamreddy H, Min H, Kim JY, Yang X, Cho ES, Kim UK & Bok J. (2019). Region-specific endodermal signals direct neural crest cells to form the three middle ear ossicles. Development , 146, . PMID: 30630826 DOI.
  4. Yang F & Liu Y. (2018). Reporting and Description for Congenital Middle Ear Malformations to Facilitate Surgical Management. Ann Otol Rhinol Laryngol , 127, 717-725. PMID: 30091369 DOI.
  5. 5.0 5.1 Rodríguez-Vázquez JF, Yamamoto M, Abe S, Katori Y & Murakami G. (2018). Development of the Human Incus With Special Reference to the Detachment From the Chondrocranium to be Transferred into the Middle Ear. Anat Rec (Hoboken) , , . PMID: 29669196 DOI.
  6. Urban DJ, Anthwal N, Luo ZX, Maier JA, Sadier A, Tucker AS & Sears KE. (2017). A new developmental mechanism for the separation of the mammalian middle ear ossicles from the jaw. Proc. Biol. Sci. , 284, . PMID: 28179517 DOI.
  7. Burford CM & Mason MJ. (2016). Early development of the malleus and incus in humans. J. Anat. , 229, 857-870. PMID: 27456698 DOI.
  8. Takanashi Y, Shibata S, Katori Y, Murakami G, Abe S, Rodríguez-Vázquez JF & Kawase T. (2013). Fetal development of the elastic-fiber-mediated enthesis in the human middle ear. Ann. Anat. , 195, 441-8. PMID: 23706648 DOI.
  9. Richter CA, Amin S, Linden J, Dixon J, Dixon MJ & Tucker AS. (2010). Defects in middle ear cavitation cause conductive hearing loss in the Tcof1 mutant mouse. Hum. Mol. Genet. , 19, 1551-60. PMID: 20106873 DOI.
  10. Rodríguez-Vázquez JF. (2005). Development of the stapes and associated structures in human embryos. J. Anat. , 207, 165-73. PMID: 16050903 DOI.
  11. 11.0 11.1 Sánchez-Fernández JM, Saint-Gerons S & Sánchez del Rey A. (1992). A microanalytical study on human auditory ossicles in normal and pathological conditions. Acta Otolaryngol. , 112, 317-21. PMID: 1604999
  12. 12.0 12.1 12.2 12.3 Whyte J, Cisneros A, Yus C, Obón J, Whyte A, Serrano P, Pérez-Castejón C & Vera A. (2008). Development of the dynamic structure (force lines) of the middle ear ossicles in human foetuses. Histol. Histopathol. , 23, 1049-60. PMID: 18581276 DOI.
  13. 13.0 13.1 Yokoyama T, Iino Y, Kakizaki K & Murakami Y. (1999). Human temporal bone study on the postnatal ossification process of auditory ossicles. Laryngoscope , 109, 927-30. PMID: 10369284
  14. Minatogawa T, Kanoh N, Kumoi T & Nishimura Y. (1994). Developmental anomaly of the process of Folius. Eur Arch Otorhinolaryngol , 251, 105-8. PMID: 8024756
  15. Thompson H, Ohazama A, Sharpe PT & Tucker AS. (2012). The origin of the stapes and relationship to the otic capsule and oval window. Dev. Dyn. , 241, 1396-404. PMID: 22778034 DOI.
  16. Anson BJ. Karabin JE. and Martin J. Stapes, fissula ante fenestram and associated structures in man: I. From embryo of seven weeks to that of twenty-one weeks (1938) Arch. Otolaryng. 28: 676-697.
  17. Anson BJ. Karabin JE. and Martin J. Stapes, fissula ante fenestram and associated structures in man: II. From Fetus at Term to Adult of Seventy (1938) Arch. Otolaryng. 28: 676-697.
  18. Beaton LE. and Anson BJ. Adult form of the human stapes in the light of its development (1940) Q Bull Northwest Univ Med Sch. 14(4): 258–269. PMC3802306
  19. Cauldwell EW. and Anson BJ. Stapes, fissula ante fenestram and associated structures in man III. from embryos 6.7 to 50 mm in length. (1942) Arch. Otolaryng. 36: 891-925.
  20. Anson BJ. and Cauldwell EW. Stapes, fissula ante fenestram and associated structures in man: IV. From fetuses 75 to 150 mm in length. (1943) Arch. Otolaryng. 37: 650-671.
  21. Anson BJ. and Cauldwell EW. Stapes, fissula ante fenestram and associated structures in man: V . From the fetus of 160 mm to term. (1948) 48(3): 263-300.
  22. Takechi M, Kitazawa T, Hirasawa T, Hirai T, Iseki S, Kurihara H & Kuratani S. (2016). Developmental mechanisms of the tympanic membrane in mammals and non-mammalian amniotes. Congenit Anom (Kyoto) , 56, 12-7. PMID: 26754466 DOI.
  23. 23.0 23.1 Rodríguez-Vázquez JF, Mérida-Velasco JR & Verdugo-López S. (2010). Development of the stapedius muscle and unilateral agenesia of the tendon of the stapedius muscle in a human fetus. Anat Rec (Hoboken) , 293, 25-31. PMID: 19899117 DOI.


Tucker AS. (2017). Major evolutionary transitions and innovations: the tympanic middle ear. Philos. Trans. R. Soc. Lond., B, Biol. Sci. , 372, . PMID: 27994124 DOI.

Takechi M, Kitazawa T, Hirasawa T, Hirai T, Iseki S, Kurihara H & Kuratani S. (2016). Developmental mechanisms of the tympanic membrane in mammals and non-mammalian amniotes. Congenit Anom (Kyoto) , 56, 12-7. PMID: 26754466 DOI.

Chapman SC. (2011). Can you hear me now? Understanding vertebrate middle ear development. Front Biosci (Landmark Ed) , 16, 1675-92. PMID: 21196256

Takechi M & Kuratani S. (2010). History of studies on mammalian middle ear evolution: a comparative morphological and developmental biology perspective. J. Exp. Zool. B Mol. Dev. Evol. , 314, 417-33. PMID: 20700887 DOI.


Laufer AS, Metlay JP, Gent JF, Fennie KP, Kong Y & Pettigrew MM. (2011). Microbial communities of the upper respiratory tract and otitis media in children. MBio , 2, e00245-10. PMID: 21285435 DOI.

Rodríguez-Vázquez JF. (2005). Development of the stapes and associated structures in human embryos. J. Anat. , 207, 165-73. PMID: 16050903 DOI.

Search PubMed

May 2010 "Middle Ear Development" All (2368) Review (226) Free Full Text (272)

Search Pubmed: Middle Ear Development | Ossicle Development | Malleus Development | Incus Development | Stapes Development | Tympanic Membrane Development

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

Glossary Links

Glossary: A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | Numbers | Symbols | Term Link

Cite this page: Hill, M.A. (2024, June 19) Embryology Hearing - Middle Ear Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Hearing_-_Middle_Ear_Development

What Links Here?
© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G