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Veterinary Medicine Year 2 > ENI - Ear > Flashcards

ENI - Ear Flashcards

1
Q

List the functions of the ear

A
  • Locate directional source of sound
  • Collect sound waves and conduct to inner ear
  • Transduction and transmission of impulses to brain
  • Balance and positional sense
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2
Q

What are the 3 levels of the ear?

A
  • External
  • Middle
  • Inner
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3
Q

Describe the anatomy of the auricular cartilage

A
  • Flattened distally
  • Ridged proximally to form anthelic and tragus
  • Changes from cone shaped to tube shaped proximally, concha
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4
Q

Describe the anatomy of the scutiform cartilage

A
  • Rostromedial

- Function is support

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5
Q

What are the limits of the external ear?

A

Pinna and external ear canal (external auditory meatus) down to tympanic membrane (ear drum)
- L shaped

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6
Q

Describe the anatomy of the annular cartilage

A
  • Ring shaped

- Attaches other cartilages to bone of bulla

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7
Q

Describe the anatomy of the acoustic process

A
  • Ligamentous attachments to skull

- Attaches to cartilages

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8
Q

What is the vascular supply to the external ear?

A
  • Auricular arteries (from internal carotid)

- Venous drainage to internal maxillary vein

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9
Q

Describe the innervation of the external ear

A
  • Motor nerves to auricular muscles (auriculopalpebral branch of CN VII facial)
  • Sensory: branch of CN V trigeminal, cervical segmental C2
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10
Q

What structures are adjacent to the external ear?

A
  • Parotid salivary gland
  • Blood vessels (auricular artery, superficial temporal arteries, branches of external carotid, external maxillary vein)
  • Nerves
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11
Q

What nerves run close to the external ear?

A
  • Facial nerve (rostroventrial to horizontal canal)

- Auriculotemporal branch of mandibular portion of trigeminal nerve (rostral to vertical canal)

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12
Q

Describe the integumentary covering of the external ear

A
  • Tightly adherent, except Henri’s pocket on caudal pinnal edge
  • Thin, squamous stratified keratinising epidermis
  • Thin dermis containing adnexal structures
  • Hair follicles variable density
  • Glands present
  • Connective tissue underneath and tehn cartilage
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13
Q

Describe the glands of the external ear

A
  • Sebaceous more prominent distally
  • Apocrine, ceruminous
  • Increased density proximally
  • Sebaceous glands closer to epidermis than apocrine
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14
Q

Describe the histological appearance of the sebaceous glands of the external ear

A

Large foamy appearance, lipid containing cells

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15
Q

Describe the histological appearance of the apocrine glands of the external ear

A
  • Simple cuboidal epithelium

- Watery secretion

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16
Q

Compare the types of secretion in different parts of the external ear canal

A
  • Distally more lipidy (sebaceous glands)

- Proximally more watery (apocrine glands)

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17
Q

Describe hair within the external ear

A
  • Differs by breed and species
  • Sebaceous glands associated with follicles
  • Number of hairs in ear canal does not equate to ear disease
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18
Q

Describe the tympanic membrane

A
  • Epithelial
  • Boundary betwen external and middle ear
  • Stratified keratinising epithelium laterally (outer part)
  • Thin lamina propria
  • Cuboidal mucosal epithelium medially (middle ear side)
  • Scattered secretory goblet cells
  • Pars flaccida and pars tensa present
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19
Q

Describe the normal cleaning mechanism of the tympanic membrane

A
  • Migration of cells centripetally from middle at level of stratum granulosum
  • Upward epithelial migration proceeds distally
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20
Q

Describe the pars flaccida of the tympanic membrane

A
  • Thicker part
  • Dorsorostrally
  • Adjacent to malleus
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21
Q

Describe the pars tensa of the tympanic membrane

A
  • Thinner
  • Centrally
  • Translucent
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22
Q

Describe the appearance of the malleus at the level of the tympanic membrane

A
  • Manubrium of malleus visible
  • C-shaped
  • Closely associated with collagen in lamina propria
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23
Q

Describe the middle ear

A
  • Tympanic cavity in tympanic bulla
  • Contains auditory ossicles
  • Connected to nasopharynx via eustachian tube
  • 3 compartments
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24
Q

What are the 3 compartments of the the middle ear?

A
  • Epitympanum
  • Mesotympanum
  • Hypotympanum
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25
Q

Describe the epitympanum

A
  • Dorsal, smallest compartment

- Contains malleus and incus

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26
Q

Describe the mesotympanum

A
  • Tympanic memrbane laterally
  • Bony promontory medially
  • 3rd ossicle stapes attached to oval window
  • Round window and opening to auditory tube
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27
Q

Describe the hypotympanum

A
  • Fundus

- Blind ending cavity

28
Q

What is unique about the hypotympanum of the cat

A

Incomplete bony septum dividing hypotympanum

29
Q

Describe the anatomy of the auditory ossicles

A
  • Supported by ligaments and muscles

- Variation of relative position affects tension of tympanic membrane

30
Q

Describe the integument of the middle ear

A
  • Cuboidal to columnar epithelial lining

- Mucosal origin, secretory goblet cells

31
Q

Describe the location of the eustachian tube

A

Runs dorsolaterally/ventromedial to the nasopharynx

32
Q

Describe the integument of the eustachian tube

A
  • Pseudostratified, ciliated, columnar epithelium
  • Density increases towards nasopharynx
  • Scattered goblet cells
  • More prominent at tympanic cavity end
33
Q

What is the function of the goblet cells in the eustachian tube?

A
  • Surfactant secretion to keep tube patent

- Lecithin, lipids mucopoysaccharides

34
Q

What nerves run close to the wall of the bulla?

A
  • Facial nerve CNVII
  • Branches of facial nerve and vagus CNX
  • Post-ganglionic fibres of cervical sympathetic trunk
35
Q

Describe the path of the facial nerve CNVII with relation to the bulla

A
  • In facial canal in petrous temporal bone
  • Exposed in dorsal cavity
  • Then exits via stylomastoid foramen
36
Q

Describe the path of the branches of the facial nerve and the vagus CNX nerves in relation to the bulla

A
  • Form tympanic nerve

- Transverse cavity to form lingual nerve and pre-ganglionic parasympathetic fibres to salivary glands

37
Q

Describe the post-ganglionic fibres of the cervical sympathetic trunk in with respect to the bulla

A
  • Dorsomedial wall of tympanic cavity
  • In cat runs in dividing septum
  • Joins CNIV to eye
  • Diseases leads to Horner’s syndrome
38
Q

Describe the inner ear

A
  • Contained within petrous temporal bone
  • Cochlea, vestibule and semicircular canals
  • Encased in bony labyrinth of petrous temporal bone
39
Q

What functions is the inner ear responsible for?

A
  • Hearing
  • Balance
  • Position and rotation of head in relation to gravitational forces
40
Q

What methods can be used to investigate ear disease?

A
  • Cytology of external ear
  • Otoscopy
  • Radiography
41
Q

Describe the normal microflora of the external ear

A
  • Same as skin
  • Staphylococci
  • Malassezia in particular
42
Q

Discuss the role of cerumen in aural health

A
  • Provides protective antimicrobial layer

- Contains immunoglobulins and exfoliated cells

43
Q

Describe the composition of cerumen

A
  • Exfoliated cells (squames discarded and shed as part of cerumen)
  • Sebaceous secretions (high lipid content, various classes of lipids)
  • Ceruminous (apocrine) gland secretions (more aqueous)
  • Immunoglobulins IgA, IgG, IgM (mostly IgG)
44
Q

Describe the role of epithelial cell migration in aural health

A
  • Carries exudate in ear to surface removing cerumen and debris
  • Epithelial cells move laterally from centre of tympanic membrane to periphery
  • Then desquamate to contribute to production of cerumen
  • May be impeded by disease
45
Q

Give an example of how middle ear disease may occur

A
  • Producing too much mucus

- Can fill middle ear with fluid

46
Q

What are the consequences of a ruptured tympanic membrane in terms of flushing the ear?

A
  • If ruptured, need to put in ET tube
  • If not, fluid will go down eustachian tube into pharynx
  • Will drown patient
47
Q

Define otitis

A

Inflammation of the ear

- Can be distinguished as externa, media and interna

48
Q

Describe radiographic imaging of the ears

A
  • Dosoventral, rostrocaudal, open mouth
  • Allows comparisons between left and right sides
  • In each view, tympanic bulla will be superimposed on other structures
49
Q

Describe the categories that risk factors for ear disease are subdivided into

A
  • Primary factors: initiate inflammation in a normal ear
  • Predisposing factors: increase risk of otitis externa but don’t cause it on their own
  • Secondary factors: do not induce, but prevent resolution of the disease once established
50
Q

Give examples of primary risk factors for ear disease

A
  • Allergic dermatitis (atopic dermatitis)
  • Grass awns
  • Otocariasis
  • Ectoparasites
  • Foreign bodies
  • Keratinsisation disorders
51
Q

Give examples of predisposing factors for ear disease

A
  • Overtreatment (e.g. antibiotics)
  • Ear pinnae and canal conformation
  • increased moisture
  • Trauma
  • Obstruction
  • Ear canal stenosis
  • Tympanic membrane perforation
52
Q

Give examples of secondary risk factors for ear disease

A
  • Opportunistic infection

- Yeast and bacteria

53
Q

What are the indications for carrying out radiography of the tympanic bullae?

A
  • Persistent otitis externa
  • Signs of otitis media including head tilt
  • Swellings assocaited with eithe rinfection or neoplasia
  • Abnormalities of TMJ e.g. dislocation, dysplasia
54
Q

What is the greatest cause of obstruction in radiography of the tympanic bullae?

A

Body of mandible

55
Q

Describe the positioning for open-mouthed rostrocaudal imaging of the tympanic bullae of the dog

A
  • Dorsal recumbency, pulls and secure forelimbs caudally
  • Flex neck at atlanto-occipital joint
  • Hard palate roughly vertical to cassette, nose pointing cranialy so hard palate and beam form 30degree angle
  • Tongue against lower jaw, secure head
  • Lower jaw exteneded and secured caudally with bandage
  • Ensure no axial rotation
  • Remove ET tube prior to exposure
56
Q

What is teh centring for open-mouthed rostrocaudal radiography of the tympanic bullae in the dog?

A

The base of the tongue

57
Q

What is the collimation for open-mouthed rostrocaudal radiography of the tympanic bullae in the dog?

A
  • Cranial: interpupillary line
  • Caudal: in line with chin
  • Lateral: outer skin surfaces
58
Q

Describe radiographic changes that occur with otitis media

A
  • Increased opacity of normally air filled bulla
  • Thickening of bulla wall
  • Sclerosis of petrous temporal bone
  • Rarely increased size of bulla
  • Ossification of horizontal canal cartilage
59
Q

Describe the radiographic changes that may occur with neoplasia of the ear

A
  • Lysis and distortion of wall of bulla

- Soft tissue swelling of adjacent region

60
Q

What are the components of an aural examination?

A
  • Assessment of external ear: pinnae, external acoustic meatus
  • View from outside
  • Palpation of auditory meatus
  • Look for erythema, exudate, odour, chronic thickening or lichenification
  • Otoscopy
61
Q

What may be seen on otoscopy?

A
  • Erythema or hyperplasia of mucosa
  • Ulceration of mucosa
  • Exudate
  • Neoplasms
  • Foreign bodies
  • Otodected cynotis (ear mite)
  • Tympanic membrane
62
Q

Describe the examination of cerumen/exudate for ear mites

A
  • Small amount of liquid paraffin on clean micro sclide
  • Sample exudate with cotton bud
  • Transfer to paraffin on slide, break up if needed
  • Place coverslip on top
  • View systematically under x4 objective
63
Q

Describe cytology of otic exudate

A
  • Cotton bud into ear canal to level of horizontal canal, sample exudate
  • Roll sample onto clean slide
  • Repeat on other ear using clean end/new bud
  • Put sample on opposite side of slide, label
  • Stain with DiffQuik
64
Q

What are the signs of damage to the facial nerve?

A

Facial paralysis

65
Q

What are the signs of damage to the vestibulocochlear nerve?

A
  • Head tilt
  • Nystagmus
  • Deafness
66
Q

What are the signs of damage to the sympathetic fibres near the ear?

A
  • Horner’s syndrome
  • Miosis
  • Ptosis
  • Enopthlamos
  • Nictitating membranes protruding
67
Q

What may the presence of rods on ear cytology commonly indicate?

A

Pseudomonas

Veterinary Medicine Year 2 (30 decks)

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