Ear Anatomy Flashcards

1
Q

What are the three parts of the ear

A

external, middle, inner ear

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2
Q

What are the 2 parts of the External Ear?

A

Pinna/Auricle and External Acoustic Meatus/ear canal

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3
Q

What are the 3 cartilages of the external ear?

A

Auricular cartilage, Annular cartilage, Scutiform cartilage

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4
Q

Describe the auricular cartilage

A

Large cartilage of the pinna and external acoustic meatus

Flat distal part- Pinna

Tubular proximal part- External acoustic meatus

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5
Q

Describe the annular cartilage

A

Small tubular cartilage

Joins auricular cartilage to osseous external acoustic meatus

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6
Q

Describe the scutiform cartilage

A

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

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7
Q

Describe the pinna

A

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

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8
Q

What is the scapha

A

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

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9
Q

What is the concha

A

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

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10
Q

What is the helix

A

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

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11
Q

What is the tragus

A

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

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12
Q

What are the incisures

A

Intertragic incisure -between antitragus and tragus

Pretragic incisure -between medial helix and tragus

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13
Q

What are the four groups of muscles of the pinna

A

Rostral Dorsal Caudal Ventral

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14
Q

Describe the muscles of the pinna and innervation

A

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

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15
Q

Describe blood supply to the pinna

A

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

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16
Q

Clin sig of Ear vasculature

A

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

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17
Q

Describe aural hematomas

A

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

18
Q

What nerves innervate the concave surface of pinna

A

Facial n - Internal auricular brr of auriculopalpebral n

Vagus n - Auricular br

19
Q

What nerves innervate the convex surface of the pinna

A

Mandibular br of Trigeminal n

C2 spinal n - Great auricular n, Great occipital n

20
Q

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

A

Cartilaginous part-
Tubular auricular, cartilage Annular cartilage

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

21
Q

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

A

Vertical part- Tubular auricular cartilage

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

22
Q

What lines the ear canal

A

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

23
Q

How to view Ear canal

A

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

24
Q

Sensory innervation to skin of ear canal

A

Facial n - cartilaginous portion

Vagus n - cartilaginous portion

Mandibular n - osseous portion, tympanic membrane

25
Describe a lateral ear canal resection
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
26
Wha structures need to be considered with lateral ear canal resection
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
27
List components of the middle ear
Tympanic membrane Ear ossicles Tympanic cavity Auditory tube (Vestibular window, Cochlear window)
28
Describe the tympanic membrane
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
29
What’s visible otoscopically of the tympanic membrane?
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
30
Describe the ear ossicles
3 small bones of the middle ear -malleus, incus, stapes Transmit vibrations from the tympanic membrane to the inner ear
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
tympanic bulla petrous temporal bone tympanic membrane vestibular window Ostium rostroventrally facial glossopharyngeal nerves post ganglionic sympathetic
32
Tympanic cavity species differences
Tympanic cavity is partially divided by the septum bullae More prominent and notable in the cat
33
clinical importance of nerves traveling in tympanic cavity
Can be affected by otitis media interna Ear infection can cause horner's syndrome
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
tympanic cavity nasopharynx equalization of pressure tympanic bulla musculotubular canal rostral tympanic bulla ventral
35
Describe the internal ear purpose and location
Organ for hearing and balance Located within the petrous part of the temporal bone
36
What are the two labyrinths of the internal ear and what do they contain
Osseous labyrinth: Cochlea, Vestibule, Semicircular canals Membranous labyrinth: Cochlear duct, Sacculus, Utriculus, Semicircular ducts
37
What are the fluid components of the internal ear
Endolymph (fills membranous part) Perilymph (fills osseous part)
38
Nerves to internal ear
CN 8, CN 7
39
Where does the vestibulocochlear nerve divide into the cochlear and vestibular part
At the osseous labyrinth
40
What does the cochlear nerve innervate and purpose
innervates the cochlear ducts for hearing
41
What does the vestibular nerve innervate and purpose
innervates the sacculus, utriculus, and semicircular ducts for balance
42
Where does CN 8 vestibulocochlear n travel
Travels from brainstem through internal acoustic meatus into petrous part of the temporal bone