1. In the name of God
The Ear
Dr. Zahiri

2. The Ear is responsible of hearing and balance
This organ is composed of three regions, external ear, middle ear, and inner ear
External ear received sound and translated sound into mechanical vibrations
Middle ear amplified mechanical vibrations
Inner ear regulate hearing and maintain equilibrium
Vestibulocochlear nerve transmits sensory signals to the brain
Dr. Maria Zahiri

3. Dr. Maria Zahiri

4. External Ear The external ear is composed of : the auricle or pinna
external auditory meatus
tympanic membrane
Dr. Maria Zahiri

5. Inner 2/3 of meatus is composed of bone External auditory meatus
The auricle is composed of a plate of elastic cartilage covered by thin skin
The initial segment of external auditory meatus is composed of elastic cartilage that is continuous with the cartilage of pinna
Inner 2/3 of meatus is composed of bone
External auditory meatus
is covered with thin skin
containing hair, sebaceous
glands and modified sweat
glands known as ceruminous
glands that secrete earwax
Dr. Maria Zahiri

6. Dr. Maria Zahiri

7. Cerumen
A mixture of relatively viscous secretions from the sebaceous glands and non-viscous secretion from the ceruminous glands (modified apocrine glands)
Dr. Maria Zahiri

8. External surface of tympanic membrane is covered by a thin epidermis
Tympanic membrane covers the deepest end of the external auditory meatus
External surface of tympanic membrane is covered by a thin epidermis
internal surface is lined by a simple squamous or low cuboidal epithelium
The core of membrane is composed of a thin layer of connective tissue elements
Dr. Maria Zahiri

9. Dr. Maria Zahiri

10. Middle Ear
The tympanic cavity which is an air filled space in temporal bone is covered by simple squamous or low cuboidal epithelium
Three auditory ossicles located here are composed of compact bone
The ossicles covered by simple squamous epithelium and articulate together by synovial joints
Two skeletal muscles control motion between bone
Auditory (Eustachian) tube is lined by pseudostratified columnar ciliated epithelium
Dr. Maria Zahiri

11. Dr. Maria Zahiri

12. Eustachian (Auditory) Tube
Wall is bone closest to tympanic cavity, replaced by elastic cartilage except in nasopharynx where it becomes hyaline cartilage
Lined with ciliated epithelium, goblet cells and diffuse lymphoid tissue.
Equalizes air pressure between the tympanic cavity and the external environment. Walls normally closely apposed but open during swallowing and yawning.
Dr. Maria Zahiri

13. Inner Ear Bony Labyrinth
Inner ear is composed of bony labyrinth and membranous labyrinth
Bony Labyrinth
is part of temporal bone that is lined by endosteum
Perilymphatic space separated bony labyrinth from membranous labyrinth which is filled by a clear fluid known as perilymph
Membranous labyrinth suspended in this fluid
Central region of bony labyrinth is called vestibule that is between posteriorly placed semicircular canals and anteriorly placed cochlea
Dr. Maria Zahiri

14. INNER EAR – A membranous labyrinth filled with endolymph
inside a bony labyrinth filled with perilymph
Dr. Maria Zahiri

15. Bony Labyrinth
Dr. Maria Zahiri

16. Components of the Bony Labyrinth
Vestibule: Contains Utricle and Saccule
Semicircular Canals: Extend from vestibule. Superior, lateral and posterior at right angles to one another. Contains the semicircular ducts. At one end of each is a dilatation, the ampulla.
Cochlea: Coils like a snail around a central pillar of bone, the modiolus.
The cochlear duct rests upon a partial shelf of bone projecting from the modiolus, the osseous spiral lamina
Dr. Maria Zahiri

17. Helicotrema
Modiolus
Osseous
Spiral
Lamina
Dr. Maria Zahiri

18. Membranous Labyrinth
Dr. Maria Zahiri

19. Sensory Regions
Dr. Maria Zahiri

20. Saccule and Utricle
Saccule and Utricle are composed of a thin vascular CT that its inner side is lined by a simple squamous to low cuboidal epithelium consists of light and dark cells
Light cells may play a role in absorption of endolymph and dark cells control its composition
Macula is a thickened specialized region of epithelium which acts as receptor for linear acceleration
Maculae are composed of neuroepithelial cells (type I) and hair cells (type II) and supporting cells
Type I and II cells have a single kinocillium and about 100 stereocilia

21. Saccule and Utricle
Stereocilia arranged in rows according to length, the longest being nearest to kinocilium
Supporting cells maintain the hair cells and contribute to production of endolymph
Stereocilia of neuroepithelial cells are embeded in a thick gelatinous, glycoprotein membrane known as otolithic membrane
Surface of this membrane is contains calcium carbonate crystals known as otoliths or otoconia
Type I and II cells innervated by vestibular branch of VIII cranial nerve
Type I: Large cup-shaped ending
Type II: Many afferent endings

23. Dr. Maria Zahiri

24. Saccule & Utricle
Dr. Maria Zahiri

26. Semicircular ducts
These are located in semicircular canal, arising from utricle
Near the utricle ducts expanded and form ampullae which are contain cristae ampullares
Crista ampullaris is composed of a ridge that covered by sensory epithelium consists of supporting cells and neuroepithelial hair cells ( type I and II )
Hair cells do not lie on basal lamina and are located between supporting cells
Cupula is similar to otolithic membrane but it is cone shape and has not otolith

29. Cochlear Duct
Cochlear duct contains organ of Corti that is responsible to responds to sound
Modiolus has a lateral projection which is known as osseous spiral lamina
Periosteum of the osseous spiral lamina forms spiral limbus
Spiral organ of Corti supported by the thickened periosteum of the cochlea that is called spiral ligament
Basilar membrane is a thin membrane that extends between the spiral ligament and the osseous spiral lamina

30. Dr. Maria Zahiri

32. Dr. Maria Zahiri

33. Basilar membrane support the organ of Corti and its vibration induced by disturbances in the perilymph detected by hair cells of the organ of Corti
Vestibular membrane extends across the cochlear duct
Vestibular Membrane is composed of two layers of flattened squamous epithelial cells
Stria vascularis is a pseudostratified epithelium that contains intraepithelial plexus of capillaries
Stria vascularis extends between vestibular membrane and the spiral prominence
Spiral prominence is a protuberance covered by epithelium that continuous with stria vascularis and continues onto basilar membrane that is called cells of Claudius

36. COCHLEA DUCT
Scala Media is the space within the triangular shaped cochlear duct. It is filled with endolymph
The cochlear duct and the spiral lamina divide the cochlea into two additional spaces:
The scala vestibuli and the scala tympani. Both are filled with perilymph and are contiuous with one another at the helicotrema
Dr. Maria Zahiri

37. Cells of Organ of Corti
It is composed of inner and outer hair cells and supporting cells
Supporting cells consist of: inner and outer pillar cells, inner and outer phalangeal cells and cells of Hensen
Inner hair cells are neuroepithelial and responsible in the reception of sound
They are arranged in a single row along the entire length of cochlea
Their stiff stereocilia arranged in a W-shaped formation but no kinocilium
At the base of each hair cell are efferent and afferent nerve endings that transmit impulses to the bipolar neurons of the spiral ganglion.

39. Cochlear Duct
Dr. Maria Zahiri

40. Cells of Organ of Corti
Outer hair cells are also neuroepithelial are three or more rows located between outer phalangeal and outer pillar cells
Inner and outer pillar cells rest on basilar membrane, enclose the inner tunnel of Corti
Inner and outer phalangeal cells are intimately associated with the inner and outer hair cells respectively
They support nerve fibers that synapses with the hair cells

41. Tectorial Membrane Tectorial membrane overlies the tip of hair cells
It is composed of glycoproteins

43. Endolypmphatic Duct and Sac
Simple squamous epithelial lining becoming columnar near the sac.
Columnar epithelium has two cell types, one with microvilli, pinocytotic vesicles and vacuoles.
This cells may be responsible for the absorption of endolymph and endocytosis of foreign materials
Dr. Maria Zahiri

44. Helicotrema – along tympani and dissipation through round window
Path of sound waves – in through oval window – up scala vestibuli – through
Helicotrema – along tympani and dissipation through round window
Dr. Maria Zahiri

45. Dr. Maria Zahiri
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