1. Otic; Vestibular; Auditory
The Ear
Otic; Vestibular; Auditory

2. External Ear (contains air); Middle Ear (contains air); Inner Ear (contains fluid)
pinna
tympanic membrane
external auditory
canal

3. I M S Middle Ear: the ossicles Malleus (tympanic membrane) Incus
Stapes (oval window) M I S

4. Middle Ear M I air E. A. TM Canal air AT air
pharyngotympanic (auditory) tube, connected to nasopharynx region
of the throat; functions in equalizing pressure.
Normally this tube is flattened and closed, but swallowing or yawning causes it to open temporarily to equalize the pressure of the middle ear cavity with external air pressure. M I S TM
E. A.
Canal
Middle Ear
air
air AT
air

5. Inner Ear

6. Inner Ear
Two layers:
Bony labyrinth filled with an aqueous fluid called perilymph. The three subdivisions of the bony labyrinth are the
semicircular canals
vestibule
cochlea.
Membranous labyrinth filled with endolymph. This is a second membrane-bound system suspended in the perilymph. The three subdivisions of the membranous labyrinth are:
the semicircular ducts
the Utricle and the Saccule
the cochlear duct.

7. (semi-circular ducts)
Inner Ear
Semi-circular canals
(semi-circular ducts) C U V S
Vestibule
(utricle & saccule)
Cochlea
(cochlear duct)

8. Inner Ear: membranous labyrinth

9. Vestibular System: Dynamic Equilibrium
Semicircular canals: (1) lateral (horizontal), (2) posterior (sagittal), and (3) anterior or superior (frontal) canals.
Contain membranous semicircular ducts, at the base of which is an enlarged region, the ampulla.
Each ampulla contains a crista, consisting of a tuft of hair cells covered with a gelatinous cap, or cupola.
Circular movements of the head move the endolymph in the semicircular ducts, which pushes the cupola in the ampullae, and causes the hair cells to fire impulses, which travel down the vestibulocochlear cranial nerve VIII to the brain.

10. V Inner Ear Semi-circular canals C U S vestibule cochlea
anterior (frontal) canal
Semi-circular canals C U
lateral (horizontal) canal V S
posterior (sagittal) canal
vestibule
cochlea

11. Semi-circular canals contain membranous semi-circular ducts, at the base of which is an enlarged region, the ampulla.
Each ampulla contains a crista, consisting of a tuft of hair cells covered with a gelatinous cap, or cupola.
ampulla

12. Each ampulla contains a crista (hair cell).
Hair cells in ampullae
Each ampulla contains a crista (hair cell).
Circular movements of the head move the endolymph in the semicircular ducts, which pushes the cupola in the ampullae, and causes the hair cells to fire impulses, which travel down the vestibulocochlear cranial nerve VIII to the brain.

13. Semicircular canals
Anterior
‘YES’
Lateral
‘NO’
Posterior
TILTING HEAD

14. Vestibular System: Static Equilibrium.
The vestibule contains receptors (maculae) that respond to static equilibrium. The maculae respond to gravitational pull, thus providing information on which way is up or down.
The maculae are located in the utricle and saccule.
Maculae consist of hair cells whose cilia project into gelatinous mass containing small grains of calcium carbonate (otoliths).
As the head moves, the otoliths also move, thus triggering nerve impulses in cranial nerve VIII.

15. Vestibular System: Static Equilibrium
maculae

16. Vestibular System: Static Equilibrium.
maculae and otoliths

17. Vestibular System: Static Equilibrium
macular function
TILT HEAD BACK

18. Vestibular branch VIII

19. Sense of Hearing
The cochlear duct separates the cochlea into an upper chamber (scala vestibuli) and a lower chamber (scala tympani). The scala vestibuli terminates at the oval window. The scala tympani terminates at the round window.
The cochlear duct supports the organ of corti, which contains the receptors for hearing. These are sensory hair cells resting on the basilar membrane; the cilia of these hair cells project up into the tectorial membrane, and the nerve endings of the cochlear division of the vestibulocochlear cranial nerve VIII, which sends impulses to the auditory association centre in the temporal lobe of the brain.

20. cochlea

21. cochlea

22. Cochlear chambers cd td sv cd td

23. Organ of Corti tm bm tm bm

24. Organ of Corti

25. Auditory Pathway

26. Summary of the Inner Ear
Bony Labryinth (Perilymph)
Dynamic Static Hearing
Equilibrium Equilibrium
Semicircular canals Vestibule Cochlea
Oval Window: Scala vestibuli
Round Window: Scala tympani
Membranous Labryinth (Endolymph)
Semicircular ducts Utricle & Saccule Cochlear Duct
Ampullae with cristae Maculae Organ of Corti
Cupola with hair cells Otoliths Tectorial membrane, hair cells with hair cells Basilar membrane