Ear
General
Anatomy


Topic Completed: 1 October 2013

Minor changes: 12 February 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Ear anatomy [title]


Nat Pernick, M.D.
Page views in 2019: 487
Page views in 2020 to date: 239
Cite this page: Pernick N. Anatomy. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/earnormalanatomy.html. Accessed August 8th, 2020.
Definition / general
  • Sense organ for hearing and balance
  • Divided into external ear, middle ear and temporal bone and inner ear
  • External ear conducts sound vibrations to tympanic membrane; middle ear conducts sound to auditory portion of inner ear
External ear

Definition / general:

  • Consists of pinna (auricle) leading into external auditory canal which ends at tympanic membrane
  • Pinna: develops from fusion of auricular hillocks, themselves from first and second branchial areas; helix is prominent rim; antihelix is prominence that is parallel with and in front of helix
  • External auditory canal: S shaped passage, 2.5 cm long, develops from remnant of first branchial groove; has outer cartilaginous portion and inner osseous portion
  • Tympanic membrane: develops from first and second branchial pouches and first branchial groove


Diagrams / tables:

Images hosted on other servers:
Missing Image

Lateral surface of pinna

Missing Image Missing Image

External and middle ear

Missing Image

External, middle and inner ear

Missing Image

Tympanic membrane

Middle ear

Definition / general:

  • Also called tympanic cavity
  • Filled with air (via eustachian tube); contains chain of movable bones which convey vibrations communicated to tympanic membrane across the middle ear cavity to the internal ear
  • Lateral aspect is tympanic membrane and squamous portion of temporal bone
  • Medial aspect is petrous portion of temporal bone
  • Superior aspect is tegmen tympani, a thin plate of bone separating middle ear space from cranial cavity
  • Inferior aspect is thin plate of bone separating tympanic cavity from superior bulb of internal jugular vein
  • Anterior aspect is thin plate of bone separating tympanic cavity from carotid canal containing internal carotid artery
  • Posterior aspect is petrous portion of temporal bone containing mastoid air cells and mastoid antrum
  • Develops from invagination of first branchial pouch (pharyngotympanic tube) from primitive pharynx
  • Contains auditory ossicles (malleus, incus, stapes), eustachian tube, tympanic cavity, epitympanic recess, mastoid cavity, chorda tympani of facial nerve (cranial nerve VII)
  • Malleus and incus develop from mesoderm of first branchial arch (Meckel cartilage), stapes develops from mesoderm of second branchial arch (Reichert cartilage)
  • Connects to pharynx through Eustachian tube
  • Connects with mastoid cavity through contiguous pneumatic spaces


Diagrams / tables:

Images hosted on other servers:
Missing Image

Tympanic membrane

Missing Image Missing Image

Inner wall of middle ear

Missing Image

Eustachian tube

Missing Image Missing Image

Chain of ossicles


Missing Image

Malleus

Missing Image

Incus

Missing Image

Stapes

Missing Image

Temporal bone

Inner ear

Definition / general:

  • Located in medial (petrous) portion of temporal bone
  • Contains cochlea (sense organ for hearing) and vestibular labyrinth (sense organ for balance with membranous and osseous portions) and internal auditory canal (contains vestibulocochlear nerve, CN VIII)
  • Vestibular labyrinth contains semicircular canals, includes blind endolymphatic sac, located in petrous bone
  • Endolymphatic sac is connected to utricle and saccule by endolymphatic duct which passes along petrous bone
  • Develops before middle and external ear at end of first month of gestation


Diagrams / tables:

Images hosted on other servers:
Missing Image Missing Image Missing Image

Labyrinth

Missing Image

Cochlea and surrounding structures

Missing Image

Cochlea cross section

Missing Image

Floor of cochlea


Missing Image Missing Image

Spiral organ of Corti

Missing Image

Semicircular canal cross section

Missing Image

Endolymphatic sac (ES) and duct (ED)



Additional references:

Back to top