1.1 A and P Outer Ear

what are the different planes?

sagittal (separates left and right), coronal (separates front and back) and transverse (separates top and bottom)

anterior

toward the front

posterior

toward the back

superior

above

inferior

below

cranial

above

ventral

toward the front

dorsal

toward the back

caudal

below

lateral

toward the side

medial

toward the middle

ipsilateral vs contralateral

on the same side vs on the opposite side

superficial

toward or near the outside

deep

toward or near the middle

proximal

nearest to the point of origin

distal

farther from the point of origin

what are the 3 divisions of the peripheral auditory system?

outer ear, middle ear and inner ear

what is the fourth part of the auditory system in addition to the 3 other parts?

central auditory pathway

outer middle and inner ear have what mechanism

conductive.

Outer and middle ear are conducting sound from the environment and transmitting it into the inner ear and central auditory system.

central auditory pathway has what mechanism

sensorineural.

From inner ear to the central auditory system sound is conducted via sensorineural mechanism.

what part of the ear does CHL affect?

outer and/or middle ear

what are the key functions of the outer ear?

protection from foreign agents.

amplification and localisation of sound.

what are the key functions of the middle ear?

impedance matching.

pressure equalisation.

selective stimulation.

what are the key functions of inner ear?

filtering and transduction

what is the key function of different sound centres in the brain?

information processing

SNHL affects what part of the ear?

The inner ear and/or hair cells and neurons in the 8th nerve (auditory nerve).

what is the temporal bone and what does it contain?

organs of hearing and balance.

Also contains vasculature:

•   Internal carotid and jugular

• And contains the facial nerve

what is another fancy way of saying ear canal?

external auditory meatus

what are the 4 different parts of the temporal bone?

squamous

mastoid

tympanic

petrous

what view is image b and c looking at?

lateral view (outside looking in) for b and medial view (looking outwards) for c

what is the largest part of the temporal bone?

squamous

mastoid is the ___ and ___ part of temporal bone

thickest and lightest

what does petrous part of temporal bone contain?

organs of hearing and balance

what is the IAM?

internal auditory meatus, an internal orifice.

contains vestibular and cochlea projects into the brain (8th nerve into brain).

what is the outer ear also called?

pinna or auricle

pinna is made out of

cartilage for support and flexibility.

covered in skin.

pinna contains facial muscles which have which over the course of evolution has become what?

vestigial in humans and used in sound localisation in animals.

label missing part

triangular fossa

label missing part

cymba concha

label missing part

crus of helix

label missing part

EAM

label missing part

tragus

label missing part

anti-tragus

label missing part

lobule

label missing part

cavum concha

label missing part

anti-helix

label missing part

helix

label missing part

auricular tubercle

what view of the pinna is this?

anterior

what view of the pinna is this?

anterior

label missing part

helix

label missing part

inferior crus

label missing part

concha

label missing part

tragus

label missing part

lobule

label missing part

anti-tragus

label missing part

label missing part

antihelix

label missing part

superior crus

pinna can move also by

startle reflex or lateral eye movement

moves pinna up and back and opens canal.

pinna convolutions individuals differences have no known

function, but act as complex resonators for high frequency sounds

what is the function of the EAM?

protection of ear canal from foreign agents or objects.

amplification of sound.

localisation of sound.

EAM is made out of 2 parts:

a cartilaginous (outer 1/3) and bony part (inner 2/3)

outer 1/3 of outer ear contains

cartilage

sebaceous gland

cerumen gland

hairs

describe the cartilaginous part of the EAM anatomically its position

runs medially, upwards and posteriorly from lateral to medial

describe the bony part of the EAM anatomically its position

runs medially downward and anterior from lateral to medial

what shape is the EAM?

S shape (protective function)

sebaceous gland function

secrete oil which act as a lubricant or moisturiser.

dry skin gets cracked and becomes entry point for microbes.

ceruminous gland function

produces ear wax which is a natural antimicrobial

tiny hairs function in EAM

prevent dust form settling inside ear.

funnels wax from medial to lateral (out of canal).

what is the pinna and tragus?

The pinna (or auricle) is the visible, cartilaginous outer ear that collects sound, while the tragus is a small, cartilaginous flap in front of the ear canal opening.

Outer ear physiology describe length and width of adult ear

long (2.5 - 3.5 cm) and narrow (5-7mm).

bony part lying at an angle to the cartilaginous part.

outer ear amplification

collects and directs sound waves onto the TM or eardrum.

sound pressure increased by outer ear due to its natural resonance (concha and EAM).

natural resonant frequency of concha vs EAM

~5 kHz versus 2.5 kHz

each structure amplifies sound by how much roughly

10-12 dB at its resonant frequency

EAM amplifies sound by selectively boosting sound pressure at frequencies ~2kHz to 4kHz (within main range of human speech).

amplification is what____ specific?

frequency specific

due to resonance

dB SPL greater at TM between 2 and 5 kHz

sound localisation in humans occurs via:

timing

intensity (loudness)

spectral qualities (changes in spectral shape including reflection and diffraction via pinnas)

what is interaural timing difference or ITD

difference in the time that sound particularly at low frequencies arrives at one ear and then the other.

what is ILD

interaural loudness difference

Horizontal localisation ITD vs ILD for high and low frequency sounds

ITD - low frequency sound pressure waves arrive with different timing (L before R in the image) but at similar intensities

ILD - high frequency sound pressure waves arrive at similar times, but there is a loss in intensity from L to R

sound arriving directly in front of the nose have what ITD and ILD?

same time and intensity so localisation of sound is worse

vertical plane localisation include

pinna cues (refers to how your outer ear—called the pinna—helps you figure out where a sound is coming from) important.

add notches or peaks to signal.

selective amplification of high frequencies.

changes spectral qualities of sound signal.

greater/higher elevation (greater angle and distance above the head) of sound sources

higher frequencies boosted more

greater ability to localise

inaccuracy area is at what frequency roughly

1 to 3kHz

really bad at localising sounds from those frequencies.