1

Anatomy and Physiology

• Outer Ear

• Middle Ear

• Inner Ear

• Central Auditory System

• Vestibular System

2

3

General Anatomical Terms• Medial

– Towards the midline

• Lateral– Away from the

midline

• Superior– Upper or above

• Inferior– Lower or below

• Proximal– Toward a

reference point• Distal

– Away from a reference point

• Anterior– In front

• Posterior– In back

4

General Anatomical Terms

• Unilateral– Same side

• Contralateral– Opposite side

• Bilateral– Both sides

• Binaural– Both ears

• Decussate– Cross over

5

General Anatomical Terms

• Coronal Plane. – In humans aka

frontal view

• Sagittal Plane. – Side view

• Transverse Plane. – Top or horizontal

view

6

Cross Section

7

Cross Section (outer ear)

8

Cross Section (middle ear)

9

Cross Section (inner ear)

10

Cross Section (central pathways)

11

Temporal Bone

• Contains outer, middle and inner ears

• Articulates with parietal, occipital, frontal, and sphenoid bones.

• Densest bone in body

12

Temporal Bone

• Squamous Portion. Helps enclose cranial cavity.

• Mastoid Process. Contains air cells.

• Zygomatic Process. Forms the zygomatic arch. Connects with zygomatic bone.

13

Temporal Bone

• Petrous portion (not shown). Located at the base of the skull between the sphenoid and occipital bones. Houses inner ear and internal auditory canal (IAC connects inner ear with brainstem). Levator palatini muscle is attached to Petrous portion.

• Styloid Process (not shown). Located on the medial/inferior portion of temporal bone. Attaches to several pharyngial muscles.

14

Outer Ear

15

Outer Ear

• Pinna (auricle)

• External Auditory Meatus (ear canal)

16

Outer Ear

• Pinna (auricle)– Covered with skin and composed mostly of

cartilage with exception of the lobe.– Temporalis muscle that is found posterior

and superior to pinna also helps secure pinna.

– Sebaceous glands are found under skin.

17

Pinna

18

Pinna (concha)

19

Pinna (photo)

20

Pinna (helix)

21

Pinna (helix)

22

Pinna (lobe)

23

Pinna (tragus)

24

Pinna (scaphoid fossa)

25

Pinna (triangular fossa)

26

Pinna (anti-helix)

27

Pinna (anti-tragus)

28

Pinna (Darwin’s tubercle)

29

Pinna (inter-tragal notch)

30

External Auditory Meatus (EAM)

• EAM is approximately 2.5 cm (1”) long from entrance of concha to tympanic membrane (TM) posterior-superior and 3.1 cm (1.2”) anterior-inferior.

• Slopes slightly downward from TM to concha and is S shaped.

• Transverse view shows that EAM is angled slightly forward.

• See next two slides to visualize.

31

External Auditory Meatus

32

External Auditory Meatus

33

EAM (cartilaginous portion)

34

EAM (osseous portion)

35

EAM (sebacious & cerumenous glands)

36

37

38

EAM (isthmus)

39

Function of Outer Ear

• Summary– Collects sound and provides pathway– Protects TM – Keeps at a constant temperature and

humidity– Helps us localize on vertical plane– Resonates in high frequencies

40

Function of Outer Ear

• Collects sound and provides pathway– Because Concha is larger than TM the

outer ear acts like a funnel and slightly increases SPL at TM.

41

Function of Outer Ear

• Protects Tympanic Membrane– S shape provides physical protection– Cerumen and sweat lubricate EAM and help expel

debris.

– Hair follicles are tilted to concha discourage debris from entering.

42

Function of Outer Ear

• Keeps TM at a constant temperature and humidity.

43

Function of Outer Ear• Localizes on Vertical Plane.

– Undulations and differences in cartilage of pinna cause a sound shadow as well as antiresonances between 6000-12000 Hz.

– These are important for front-back localization.

44

Function of the Outer Ear• Ear Canal Resonance

– EAM acts as a quarter wavelength resonator.– Resonance occurs at …

• EAM --- about 3400 Hz• Concha --- about 5000 Hz• Combined Effect --- about 2700 Hz.

– At 0 degrees azimuth gain is approximately 5 to 15 dB between 1500-5000 Hz. It is slightly higher at 30 to 45 degrees azimuth.

– Differs for each individual.

45

Function of the Outer Ear

• Head Related Transfer Function (EAM resonance).

46

Function of the Outer Ear

• Head Related Transfer Function (EAM resonance).

47

Summary

• Hit the Esc to return to index.