Embryology · Nervous system and senses
Ear: inner, middle and external ear !
- Process
The three parts of the ear come from different places in the embryo: a skin placode, the first pharyngeal pouch and the first two arches.
Updated 2026-11-01
See it in 3D: Cochlea · Semicircular canals · Vestibule · Malleus · Incus · Stapes · Eardrum · Auditory tube · Ear canal · Auricle · Vestibulocochlear nerve (VIII)
What it is
The inner ear forms from the otic placode of the ectoderm; the middle ear from the first pharyngeal pouch and the cartilages of arches 1 and 2; the external ear from the first pharyngeal cleft and six hillocks around it. Because their origins differ, a malformation can hit one part and spare another, which explains conductive versus sensorineural hearing loss.
Key facts
- Day 22: the otic placode appears beside the hindbrain; in week 4 it invaginates and pinches off as the otic vesicle (otocyst).
- The ventral otocyst gives the saccule and cochlear duct; the dorsal part gives the utricle, semicircular canals and endolymphatic duct.
- The cochlear duct completes its 2.5 turns by the end of week 8; the organ of Corti differentiates afterwards.
- Malleus and incus: first-arch cartilage; stapes: second arch (its footplate also gets neural crest and mesoderm).
- External acoustic meatus: first cleft; an epithelial plug fills it and recanalizes around the seventh month.
- Auricle: six auricular hillocks of arches 1 and 2; the ear rises from the neck as the mandible grows.
Structure
- Inner ear (placode ectoderm): membranous labyrinth, organ of Corti, ampullary cristae and maculae.
- Middle ear (first-pouch endoderm): tympanic cavity, auditory tube, mastoid air cells.
- Ossicles: malleus and incus (arch 1), stapes (arch 2).
- Muscles: tensor tympani (arch 1, trigeminal V3); stapedius (arch 2, facial nerve).
- Tympanic membrane: three layers, ectoderm outside, mesenchyme in the middle and endoderm inside.
- External ear: canal (first cleft) and auricle (hillocks of arches 1 and 2, with neural crest).
Step by step
- The otic placode thickens on each side of the hindbrain.
- It invaginates into the otic vesicle, which gives off cells for the vestibulocochlear ganglion.
- The vesicle divides into a cochlear (ventral) and a vestibular (dorsal) part.
- Mesenchyme forms the cartilaginous otic capsule, which later ossifies into the bony labyrinth.
- The first pouch forms the tubotympanic recess: tympanic cavity and auditory tube.
- The ossicles stay in mesenchyme until the eighth month, when the cavity expands around them.
- The hillocks fuse into the auricle and the ear rises to the side of the head.
Markers
- PAX2
- SOX2
- FGF3
- FGF10
- SHH
- HOXA2
Clinical notes
- Low-set ears: a sign of disturbed mandibular development or chromosomal syndromes.
- Defects of arches 1 and 2 (Treacher Collins) cause conductive hearing loss.
- Rubella after week 7 can spare the lens but damage the cochlea.
- A fetus responds to sound in the late second trimester.
Test yourself
Think of the answer, then tap the question to see it.
Which embryonic structure does the tympanic cavity come from?
The first pharyngeal pouch (endoderm), through its tubotympanic recess.
Which ossicle comes from the second pharyngeal arch?
The stapes; the malleus and incus come from the first arch.
Which part of the otic vesicle forms the cochlea?
The ventral part, which gives the saccule and cochlear duct.
How many layers does the tympanic membrane have, and from which germ layers?
Three: ectoderm outside, mesenchyme in the middle and endoderm inside.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
- Cochlea
- Semicircular canals
- Vestibule
- Malleus
- Incus
- Stapes
- Eardrum
- Auditory tube
- Ear canal
- Auricle
- Vestibulocochlear nerve (VIII)
Related
- Congenital hearing loss, microtia and preauricular pits
- The pharyngeal apparatus: arches, pouches, clefts and membranes
- Pharyngeal clefts and membranes: external ear and cervical sinus
- Pharyngeal pouches: tonsil, thymus, parathyroids and C cells
- First pharyngeal arch (mandibular arch) and the trigeminal nerve
- Second pharyngeal arch (hyoid arch) and the facial nerve
- First-arch syndromes: Treacher Collins and Pierre Robin sequence
- Congenital rubella syndrome
Related conditions
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Anotia/Microtia (Centers for Disease Control and Prevention, 2024); Fetal development: MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine, 2024); Langman's Medical Embryology, 13th ed., ch. 19: Ear (Wolters Kluwer, 2015).
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Representative model, for educational purposes only.