outer ear and basic acoustics

outer ear structures

pinna/auricle, EAM

purpose of outer ear

gather and funnel sound to middle ear and to protect the auditory system

parts of temporal bone

squamous, tympanic, mastoid, petrous

location of squamous

superior wall, superior-posterior wall (makes up majority of surface area)

structures the squamous portion creates

cheek and outer part of eye socket

process that arises from squamous portion

zygomatic process

location of tympanic portion

below squamous portion

structures that tympanic portion create

majority of external ear canal

process that arises from tympanic portion

styloid process

mastoid portion location

posterior

mastoid antrum

large, air-filled space within temporal bone, connects middle ear to mastoid

helps lighten the skull and pressure equalize on either side of ear drum

petrous portion location

base of skull

petrous portion structures

inner ear - cochlea, vestibular labyrinth, internal auditory meatus/canal

portion of temporal bone that forms jugular foramen

petrous portion

jugular foramen

opening within the skull where veins, arteries, and nerves come up through the skull and provide to the inner ear

tympanic ring

creates attachment point for tympanic membrane

fossa definition

shallow depression

bones that form temporal fossa

squamous, parietal, sphenoid, small portion of frontal

muscle that arises from temporal fossa

temporalis muscle

muscle that arises from mastoid process

sternocleidomastoid

muscles that arises from styloid process

stylopharyngeus, styloglossus, stylohyoid

CN VII name and significance

facial nerve, acoustic reflex has to run through VII

CN VII location

internal auditory meatus (petrous portion)

CN VIII name and significance

vestibulocohlear, hearing and balance nerve fibers

CN VIII location

internal auditory meatus (petrous portion)

CN IX name and significance

glossopharyngeal, tongue and throat

CN IX location

jugular foramen

CN X name and significance

vagus: heart, lungs, bronchi, gastrointestinal tract

CN X location

jugular foramen

CN XI name and significance

accessory: important for vestibular

CN XI location

jugular foramen

angle pinna protrudes from head

15-30 degrees

pharyngeal cleft

dips between pharyngeal arches

pharyngeal arches that auditory structures come from

arches 1 and 2

tiny muscles in middle ear space

tensor tympani and stapedius

cranial nerves important for middle ear reflexes

CN V and VII

pinna cartilage type

elastic

elastic cartilage composition

type II collagen, elastic fibers, elastin protein

layers of pinna (from innermost to outermost)

cartilage, perichondrium, skin

pericondrium

dense connective layer, contains blood vessels, gives oxygen and nutrients to cartilage

primary pinna muscles

superior auricular, anterior auricular, posterior auricular

pinna ligaments

superior ligament, anterior ligament, posterior ligament

anterior ligament connections

tragus to zygomatic process

superior ligament connections

spine to helix to bony portion of ear canal

posterior ligament connections

concha to mastoid process

primary blood supply to pinna

external carotid artery via superficial temporal artery (STA)

parts of pinna supplied by external carotid artery

anterior helix, tragus, ear lobe, scalp

parts of pinna supplied by posterior auricular artery (PAA)

posterior surface of pinna, scalp

pinna veins

superficial temporal vein, posterior auricular vein

cartilaginous portion of EAM

outer 1/3

bony portion of EAM

inner 2/3

portion where hair follicles and glands are found in EAM

cartilaginous

ear canal glands

sebaceous, ceruminous

nerves of outer ear

CN V, CN VII, CN IX, CN X, great auricular nerve, lesser occipital nerve

CN V (trigeminal nerve) outer ear areas

pre-auricular area, tragus, part of ear canal

CN VII (facial) parts of outer ear

concha, portion of ear canal

CN X (vagus) portion of outer ear

ear canal (esp medial portion), tragus

CN IX (glossopharyngeal) parts of outer ear

ear canal

great auricular nerve portion of outer ear

majority of pinna, lobe, lower portion of concha, mastoid process, skin over parotid gland

lesser occipital nerve part of outer ear

scalp posterior to pinna, upper back of neck

best frequencies for pinna

4-6kHz

ear canal acoustic resonator

around 2.5-4kHz

otomycosis

fungal infection