24 The Ear

1
24 The Ear

• I. Overview (24.20)
• II. External Ear
• III. Middle Ear
• IV. Internal Ear
• IV. Cochlea
• V. Vestibule
• VI. Semicircular Canals

2
II. External Ear

• A. Auricle (pinna) 24-20
• 1. thin skin
• 2. elastic cartilage
• B. External auditory meatus
• 1. thin skin
• a. glands
• 2. elastic cartilage
• 3. temporal bone
• C. Tympanic membrane

3
III. Middle Ear

• A. Simple squamous epithelium (24.20)
• B. Ossicles
• 1. malleus
• 2. incus
• 3. stapes
• C. Oval window
• D. Round window
• E. Auditory
• (Eustachian) tube

4
IV. Internal Ear

• A. Bony Labyrinth
• 1. vestibule (24.20)
• 2. cochlea
• 3. semicircular canals
• 4. perilymph

5
IV. Internal Ear

• E. Membranous labyrinth (24.20)
• 1. saccule
• 2. utricle
• 3. cochlear duct
• 4. semicircular ducts
• 5. endolymph

6
V. Cochlea

• A. Bony cochlea (24.20)
• 1. scala vestibuli
• a. oval window
• 2. scala tympani
• a. round window
• 3. helicotrema

7
V. Cochlea

• B. Cochlear Duct (24.24)
• 1. vestibular membrane
• 2. stria vascularis
• 3. organ of Corti

8
V. Cochlea

• C. Organ of Corti
• 1. basilar membrane (24.24)
• 2. supporting cells
• 3. internal spiral tunnel

9
V. Cochlea

• C. Organ of Corti
• 4. outer hair cells (24.24,24.25)
• a. stereocilia
• 5. inner hair cells
• 6. tectorial membrane

10
V. Cochlea

• C. Organ of Corti (24.24)
• 7. pillar cells
• a. inner tunnel

11
V. Cochlea

• C. Organ of Corti 24.24
• 8. sensory motor nerve endings
• 9. spiral ganglia
• a. bipolar sensory cells
• b. modiolus
• c. auditory nerve

12
V. Cochlea

• D. Histophysiology (24.20)
• 1. middle ear amplifies sound vibrations
• 2. oval window
• 3. scala vestibuli
• 4. vestibular membrane
• 5. organ of Corti
• 6. basilar membrane

13
V. Cochlea

• D. Histophysiology (24.24)
• 7. movement of stereocilia
• 8. generates receptor potentials
• 9. neurotransmitter released at base of hair
  cell
• 10. synaptic transmission to VIII. nerve ending

14
V. Cochlea

• D. Histophysiology (24.20)
• 11. sound vibration to scala tympani
• 12. dissipation at round window

15
VI. Vestibule

• A. Saccule utricle (24.20)

16
VI. Vestibule

• B. Maculae
• 1. supporting cells
• 2. hair cells
• 3. stereocilia cilia (24.21)
• 4. gelatinous layer
• 5. otoliths (24.22)
• 6. vestibular nerve endings

17
VI. Vestibule

• C. Histophysiology
• 1. gravity affects otoliths (24.21)
• 2. bending of stereocilia causes receptor
  potential
• 3. neurotransmitter released affecting nerve
  endings
• 4. action potential carried to CNS

18
VII. Semicircular Canals

• A. Semicircular Ducts (24.20)
• B. Ampullae

19
VII. Semicircular Canals

• C. Cristae ampullares (24.23)
• 1. supporting cells
• 2. hair cells
• 3. stereocilia
• 4. cupula
• 5. vestibular nerve endings

20
VII. Semicircular Canals

• D. Histophysiology (24.23)
• 1. acceleration of head
• 2. stimulates movement of cupula
• 3. bending of stereocilia causes
  depolarization of hair cells
• 4. neurotransmitter released from hair cells
• 5. synaptic transmission
• 6. action potential in vestibular nerve fibers

24.24