1 Anatomy and Physiology Outer Ear Middle Ear Inner Ear Central Auditory System Vestibular System

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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)

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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 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 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.