Ear Anatomy

Question 1

What are the three parts of the ear

Answer 1

external, middle, inner ear

Question 2

What are the 2 parts of the External Ear?

Answer 2

Pinna/Auricle and External Acoustic Meatus/ear canal

Question 3

What are the 3 cartilages of the external ear?

Answer 3

Auricular cartilage, Annular cartilage, Scutiform cartilage

Question 4

Describe the auricular cartilage

Answer 4

Large cartilage of the pinna and external acoustic meatus

Flat distal part- Pinna

Tubular proximal part- External acoustic meatus

Question 5

Describe the annular cartilage

Answer 5

Small tubular cartilage

Joins auricular cartilage to osseous external acoustic meatus

Question 6

Describe the scutiform cartilage

Answer 6

Boot shaped cartilage

Located on dorsum of head rostromedial to ear - imbedded in auricular muscles, fascilitates movement

Serves as attachment site of muscles of the ear

Question 7

Describe the pinna

Answer 7

also called the auricle
Flat distal portion of auricular cartilage covered with haired skin
Highly mobile

Convex caudal surface (medial, caudal)
Concave rostral surface (anterior, lateral)

Funnels sound waves to ear canal

Question 8

What is the scapha

Answer 8

The large flat inner concave surface of the pinna
Distal to the anthelix

Question 9

What is the concha

Answer 9

Funnel shaped region of pinna
Proximal to the anthelix
Surrounds the ‘conchal cavity’

Question 10

What is the helix

Answer 10

Free margin of the pinna
Lateral border of helix and medial border of helix
join at apex of the pinna
Lateral border contains ‘marginal cutaneous sac’
Medial border continued rostrally as crura

Question 11

What is the tragus

Answer 11

Projection of cartilage along rostral border of concha
Large, quadrangular
Lateral to crura of medial border of helix

Question 12

What are the incisures

Answer 12

Intertragic incisure -between antitragus and tragus

Pretragic incisure -between medial helix and tragus

Question 13

What are the four groups of muscles of the pinna

Answer 13

Rostral Dorsal Caudal Ventral

Question 14

Describe the muscles of the pinna and innervation

Answer 14

Intrinsic and Extrinsic mm
Innervated by CN VII, the facial n
Arranged in layers overtop a fat pad
Scutiform cartilage serves as an attachment for many mm

Question 15

Describe blood supply to the pinna

Answer 15

External carotid to
Caudal Auricular -> Medial, intermediate, lateral auricular

or to rostral auricular

Branches or auricular aa pass through openings in the auricular cartilage to pass from caudal to rostral

Question 16

Clin sig of Ear vasculature

Answer 16

The pinna is highly vascularized and can bleed profusely!

in pigs and ox can use ear veins for venipuncture
intermediate auricular v in ox
lateral auricular vein in pig

Question 17

Describe aural hematomas

Answer 17

Hematoma between auricular cartilage and skin due to ruptured auricular blood vessels
Caused by trauma to the ear
*Self trauma secondary to ear infections
Treatment is drainage and eliminating dead space Untreated ears fibrose and cause disfigurement

Question 18

What nerves innervate the concave surface of pinna

Answer 18

Facial n - Internal auricular brr of auriculopalpebral n

Vagus n - Auricular br

Question 19

What nerves innervate the convex surface of the pinna

Answer 19

Mandibular br of Trigeminal n

C2 spinal n - Great auricular n, Great occipital n

Question 20

Name the two parts of the external acoustic meatus based on tissue type

Answer 20

Cartilaginous part-
Tubular auricular, cartilage Annular cartilage

Osseous part-
Wall of ‘external acoustic meatus’ in tympanic part of temporal bone

Question 21

Name the two parts of the external acoustic meatus based on orientation.

Answer 21

Vertical part- Tubular auricular cartilage

Horizontal part-Tubular auricular cartilage, Annular cartilage, Bony external acoustic meatus

Question 22

What lines the ear canal

Answer 22

Lined internally with skin containing glands- Sebaceous glands, Ceruminous glands

Question 23

How to view Ear canal

Answer 23

Place otoscope in intertragic incisure
Pull pinna laterally and ventrally to straighten canal from L shape

Question 24

Sensory innervation to skin of ear canal

Answer 24

Facial n - cartilaginous portion

Vagus n - cartilaginous portion

Mandibular n - osseous portion, tympanic membrane

Question 25

Describe a lateral ear canal resection

Answer 25

Exposes ear canal for improved ventilation (don't for cases of otitis external, aids in self-cleaning of ear wax that occurs with chewing/movement) Lateral wall incised at - pretragic incisure and intertragic incisure External skin edge sutured to skin edge of ear canal

Question 26

Wha structures need to be considered with lateral ear canal resection

Answer 26

Structures adjacent to the vertical ear canal: Parotid salivary gland Brr of the facial n deep to parotid gland: Dorsal buccal br, Ventral buccal br of CN VII, Auriculopalpebral n Auriculotemporal n Brr of caudal auricular a Tributaries to caudal auricular v

Question 27

List components of the middle ear

Answer 27

Tympanic membrane Ear ossicles Tympanic cavity Auditory tube (Vestibular window, Cochlear window)

Question 28

Describe the tympanic membrane

Answer 28

Located at medial extent of osseous ear canal Separates external ear from middle ear Concave from external view Oval in shape Thin semitransparent membrane- fibrous connective tissue lined with epithelium

Question 29

What’s visible otoscopically of the tympanic membrane?

Answer 29

Two regions of membrane: pars flaccida dorsally pars tensa ventrally Attachment of malleus on inner surface of membrane “stria mallearis” The malleus curves ventrally and points rostrally

Question 30

Describe the ear ossicles

Answer 30

3 small bones of the middle ear -malleus, incus, stapes Transmit vibrations from the tympanic membrane to the inner ear

Question 31

tympanic cavity: Space bound by the ____ laterally and the _____ medially Ear ossicles extend across the dorsal tympanic cavity from_____ to ______ ______ for the auditory tube located ______ Branches of the ______ and ________, and _________ neurons pass within the tympanic cavity

Answer 31

tympanic bulla petrous temporal bone tympanic membrane vestibular window Ostium rostroventrally facial glossopharyngeal nerves post ganglionic sympathetic

Question 32

Tympanic cavity species differences

Answer 32

Tympanic cavity is partially divided by the septum bullae More prominent and notable in the cat

Question 33

clinical importance of nerves traveling in tympanic cavity

Answer 33

Can be affected by otitis media interna Ear infection can cause horner's syndrome

Question 34

Auditory tube: Tube connecting ____ to ______ Allows for _______ between the ______ and the atmosphere The ________ houses the auditory tube -extends from ____ aspect of the _____ to open on the _____ skull

Answer 34

tympanic cavity nasopharynx equalization of pressure tympanic bulla musculotubular canal rostral tympanic bulla ventral

Question 35

Describe the internal ear purpose and location

Answer 35

Organ for hearing and balance Located within the petrous part of the temporal bone

Question 36

What are the two labyrinths of the internal ear and what do they contain

Answer 36

Osseous labyrinth: Cochlea, Vestibule, Semicircular canals Membranous labyrinth: Cochlear duct, Sacculus, Utriculus, Semicircular ducts

Question 37

What are the fluid components of the internal ear

Answer 37

Endolymph (fills membranous part) Perilymph (fills osseous part)

Question 38

Nerves to internal ear

Answer 38

CN 8, CN 7

Question 39

Where does the vestibulocochlear nerve divide into the cochlear and vestibular part

Answer 39

At the osseous labyrinth

Question 40

What does the cochlear nerve innervate and purpose

Answer 40

innervates the cochlear ducts for hearing

Question 41

What does the vestibular nerve innervate and purpose

Answer 41

innervates the sacculus, utriculus, and semicircular ducts for balance

Question 42

Where does CN 8 vestibulocochlear n travel

Answer 42

Travels from brainstem through internal acoustic meatus into petrous part of the temporal bone