Outer Ear Review Flashcards
Exam 2
What are the 4 parts of the temporal bone?
mastoid portion, tympanic area, squamous portion, petrous portion
What is the organization of the somatotopic mapping of the body on the S1 and M1 areas
Head closest to the temporal lobe, arms, legs dipping into the longitudinal sulcus
CN VIII and CN VII enter or exit the brainstem at the
cerebellopontine angle
Parts of a cell and what they do:
soma (cell body containing the nucleus), dendrites (provide more area for neuron reception, branch like), axon (long cable, where impulses from the nerve travel away to be received by other neurons)
What nerves and artery course through the internal auditory canal?
CN VII facial nerve, CN VIII (cochlear division), SVN, IVN, Labyrinthine artery
Function of sodium-potassium pump for muscles and neurons
Helps to maintain equilibrium and membrane potential in cells
Maintains the gradient of a higher concentration of sodium extracellularly and a higher level of potassium intracellularly
for every 3 sodium pumped out, one potassium is pumped in
outer ear skin’s protective mechanisms:
maintains the environment in the canal and minimizes chances of infection
narrowest portion of the canal is the __
isthmus (6mm from the TM)
cerumen properties
water repelling, lubricates, antimicrobial, protects TM
what amount (in dB) does the ear canal resonate at?
(take into consideration the outer ear structures…)
17 dB!!! (2700 hz)
sound pressure gain
External ear is a passive amplifier that increases the high frequency SPL at the TM
since average length of canal is 2.5 cm, what is the resonance of the EAC? (excluding the effects of the concha/pinna)
about 3500 Hz
what does the concha do as an “end correction” of the resonant tube? What happens when the ear canal and pinna are combined?
lowers the frequencies to a peak around 2700 Hz and a peak at 5000 Hz
what do the bends in the canal do?
reduce occlusion effects (ex: deeper hearing aids make less sound waves –> our own voices sound louder
roof of ME
tegman tympani
floor of ME
jugular wall
medial wall of ME
labyrinthine wall (prominatory)
anterior wall of ME
carotid wall
3 divisions of the ear
outer, middle, inner
the outer ear includes:
pinna & ear canal
is the skin of your outer ear the same as other skin on our body?
yes
14 terms of the pinna:
helix, crus of helix, concha (cavum and cymba), triangular fossa, antihelix, crura of antihelix, darwin’s tubercle, scaphoid fossa, tragus, intertragal notch, antitragus, lobule
average length of the canal:
2.5 cm
cranial nerve innervation of the outer ear:
V VII & X (trigeminal, facial, vagus
how many turns does the canal have?
2.5
name of fissures in the cartilage of the canal:
fissures of santorini
what type of glands are in the external canal?
ceruminous (modified apocrine sweat gland, also sebacious)
which side of the canal runs longer than the other?
the floor is longer than the roof (due to obliqueness of the TM)
how do the hairs in the canal protect it?
point outward to act as a filter for incoming objects
3 neuro-reflexes
vagus, trigeminal, lymphatic
what is the vagus reflex?
causes coughing, gagging, eye watering
What is the trigeminal reflex?
“red reflex” causes thickening of the TM and vascularization (hearing aid wearing, otoscopy, otoblocks, etc)
another name for Vagus reflex
Arnold’s reflex
What is the lymphatic reflex?
slow reflex that is doe to over-wearing of aids, or an allergic reaction that causes swollen lymph and soreness around canal
more medial canal hairs lie ___ ; more lateral canal hairs lie __
flat, oblique
a sexual characteristic in males causes hairs over the tragus to become _____
thicker and longer
2 types of glands found in the outer ear
sebaceous (oil) and ceruminous (apocrine/sweat)
self cleaning ear canal function is called?
epithelial migration
2 patterns of epithelial migration:
radial (center of TM outward), and horizontal (laterally along the canal
how much does the external ear amplify sound pressure?
10 dB (resonant peak at 5,000 Hz)
inverse square law
from the sound source, as sound moves outward, it spreads out the distance it is covering and it loses intensity over that space
energy twice as far from the source is spread over four times the area, hence ¼ the intensity
tympanic membrane components:
pars flaccida, pars tensa, manubrium of the malleus, umbo, cone of light, tympanic annulus, notch of rivinus, anterior + posterior malleolar folds
quadrants of the TM
anterior superior, anterior inferior, posterior superior, posterior inferior
which quadrant has the cone of light?
anterior inferior
a right ear has the malleus at what degree?
1pm
the TM has how many layers? describe them
4 layers!
1. epithelial
2. radial fibrocartilaginous
3. concentric fibrocartilaginous
4. mucous membrane
What nerve supplies the helix, antihelix and lobule
greater auricular nerve (C2 C3) (Blue on image)
What nerve supplies concavity of concha and floor of EC?
auricular branch of vegas (CX) (purple on image)
What nerve supplies Tragus, Crus of the helix & adjacent part of helix?
Auriculotemporal nerve (branch of V3) (green on image)
What nerve supplies Auricle in depression of the concha and over its eminence?
facial nerve (C7) (Yellow on image)
What is outer half of external auditory canal made of?
supported by cartilage thin skin with dermal papillae
What nerves innovate EAM?
CN V, CN VII and CN X
What are the neural innervations for Vagus Reflux
Pacinian corpuscles
Arnold’s branch of vagus
Facial nerve
Glossopharyngeal
What nerve supplies upper part of cranial surface?
lesser occipital nerve (C2, C3) (orange in image)
What are the neural innervations for Lymphatic reflex
Facial nerve
Pacinian corpuscles
Meissner’s corpuscles
Hair follicles
What are the neural innervations for Trigeminal reflex
Pacinian and Meissner’s corpuscles
Facial sensory and motor neurons
Describe the External Ear canal
2.5 cm length
oval or elliptical shape
S-shape with 1st bend and 2nd bend
cartilaginous outer ~1/2 and boney medial ~1/2, floor
inferior wall is longer than ceiling/superior wall due to slant of TM
Why is the fissure of santorini a concern?
provide a potential path for infection or neoplasm to spread between the parotid gland and the external ear canal.
What contributes to the protective function of the ear canal?
it’s anatomy (s shape)
arrangement of the hairs (slanted laterally)
cerumen
Sympathetic and parasympathetic vascularization at TM when pressure applied in outer 1/3 of canal
trigeminal reflex
Sympathetic motor reflex caused by light touch upon the superior-inferior and anterior meatal wall
cause of vegas reflex
May appear to be due to allergies
lymphatic reflex
Evidenced by swelling of tissues and soreness while wearing a custom fitted earmold or hearing aid
lymphatic reflex
A slow reflex which may result from over-wearing of hearing aids during adaptation period
lymphatic reflex
Can cause excessive vascularization and thickening of the TM during otoscopy, otoblock insertion, and during hearing aid wearing
trigeminal reflex
Sometimes called the “red reflex”
trigeminal reflex
Also known as Arnold’s reflex or the ear-cough reflex.
vagus reflex
This reflex is evidenced by coughing, gagging, and/or watering of the eyes
vagus reflex
This reflex may be evoked during insertion of an otoblock used in making earmold impressions, cerumen removal, and rarely, with hearing aid use
vagus reflex
What is the auditory function of the outer ear?
sound pressure gain
What acts as a cavity resonator?
concha
What does cerumen contain?
lipids, proteins, free amino acids, and mineral ions
What is resonant frequency based on?
tube length
What is the average gain and resonant peak at TM due to concha? Why are the effects of the concha important?
Important in increasing high-frequency SPL at the TM with an average gain of 10 dB and a resonant peak at 4500 – 5000 Hz
acts as a cavity resonator
what is the resonant frequency for an average ear canal?
3500 Hz
The concha resonance blends with the EAM resonance, producing what?
composite curve with two peaks one at 2700 and another at 5000
