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Veterinary medicine year 2 > Ear > Flashcards

Ear Flashcards

1
Q

What are the 3 structure levels of the ear?

A

External ear
Middle ear
Inner ear

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2
Q

What makes up the external ear?

A

Pinna and external ear canal (external auditory meatus) down to the tympanic membrane

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3
Q

What makes up the middle ear?

A

Tympanic cavity in the tympanic bulla
Contains auditory ossicles
Connected to the nasopharynx?

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4
Q

Where is the inner ear?

A

Contained within the petrous temporal bone

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5
Q

What are the external ear elastic cartilages.

A

Auricular cartilage
Annular cartilage
Scutiform cartilage

All for suppport

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6
Q

Auricular cartilage

A

Flattened distally
Ridges = forms anthelix medially and the tragus laterally
Cone-> tube shape proximally

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7
Q

Annular cartilage

A

Fits within the base of the conchal tube of the auricular cartliage
Ligamentous attachments to internal auditory meatus of the temporal bonw

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8
Q

Scutiform cartilage

A

Not part of the ear canal
Within the muscles rostromedial to the canal to provide extra support

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9
Q

What innervates the external ear?

A

Auriculopalpebral branch of CN 7= Motor nerves to the auricular muscles

Sensory innervation from branch of CN V and cervical segment 2

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10
Q

What is the vascular supply to the external ear?

A

Auricular arteries from internal carotid
Venous drainage=> internal maxillary vein

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11
Q

What are the adjacent structures to the external ear?

A

Parotid salivary gland
Blood vessels
Nerves (CN VII and CN V)

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12
Q

Where is henris pocket found

A

On the caudal pinna

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13
Q

Describe the epidermis of the external ear?

A

Thin stratified squamous keratinising epidermis (including over the tympanic membrane)

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14
Q

Describe the dermis of the external ear?

A

Thin contains adnexal structures
Hair follicles in variable density on the concave pinna and down the ear canal

Dermis has glands - sebaceous= distally
Apocrine= proximally

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15
Q

Where has this histology slide been taken from?

A

Can mainly see sebaceous glands meaning it is most likely the distal portion of the external ear

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16
Q

What can be seen in this slide?

A

Apocrine gland from the external ear
Ceruminous gland (external ear)

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17
Q

What can be seen in the slides?

A

Compound hair follicles

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18
Q

What is found in the secretions of the ear canal?

A

Exfoliated cells
Sebaceous secretions
Ceruminous gland secretions
Imunoglobulins IgA IgG and IgM

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19
Q

Compare sebaceous and cermunious secretions?

A

Sebaceous= high lipid content and various classes of lipids
Ceruminous secretions = more aqueous in nature

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20
Q

What is the most common immunoglobulin in the ear canal secretions?

A

IgG

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21
Q

What is the average lipid content of the ear canal secretions?

A

50%

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22
Q

What is the role of the ear canal excretions?

A

Protection and antimicrobial layer

23
Q

How is exudate in the ear carried to the surface?

A

Via epithelial cell migration
Epi cells move laterally from centre of tympanic membrane to periphery
Desquamate = cerumen
Epi migration transports cerumen to superficial portion of each canal

24
Q

What are the properties of the tympanic membrane?

A
  • Epithelial structure
  • Boundary between the external and middle ear
  • Made of stratified squamous keratinising epithelium laterally
  • Has thin lamina propria
  • Made of simple squamous/cuboidal mucosal epithelium medially
25
Q

What is the role of the lateral epithelium of the tympanic membrane?

A
  • migration of cells centripetally from middle at the level of stratum granulosum
  • normal cleaning mechanism
  • upward epithelial migration proceeds distally
26
Q

What is contained within the medial epithelium. of the tympanic membrane?

A

Scattered secretory goblet cells

27
Q

What can be seen in this image of the tympanic membrane

A
28
Q

Where is the pars flaccida and pars tensa?

A

Pars flaccida dorsolaterally (thicker)
Pars tensa ventrally (thinner)
Manubrium of malleus- c shaped associated with collagen in lamina propria

29
Q

Function of the pars flaccida

A

Maintain a constant middle ear pressure

30
Q

Function of the pars tensa

A

plays a key role in sound conduction, with the manubrium of the malleus inserting into it and transmitting captured sound waves along the ossicular chain.

31
Q

Label the image

A
32
Q

What are the main properties of the tympanic cavity>

A
    • air filled
    • inside the bony bulla of the middle ear
    • made up of three compartments
33
Q

What are the 3 components of the tympanic cavity?

A

Epitympanum - dorsal small - auditory ossicles melleus and incus
Mesotympanum - membrane lat bony medially- 3rd ossicle stapes attached- round window opening to aud tube

Hypotympanum/ fundus

34
Q

What supports the auditory ossicles and how can they be manipulated?

A

Supported by ligaments and muscles
variation of relative position of lig and musc affect tension of the tympanic membrane

35
Q

What is the ration of the length of the malleus:incus in cats and dogs compared to men?

A

2-3x grater in cats and dogs

36
Q
A
37
Q

What structures are associated with the auditory ossicles?

A

Simple quamous to cuboidal epi linging
Auditory tube

38
Q

Auditory tube?

A

lso known as the eustachian tube

  • runs dorsolateral/ventromedial to the nasopharynx
  • pseudostratified, ciliated, columnar epithelium
  • Scattered goblet cells
    • More prominent at tympanic cavity end
    • → lecithin, lipids, mucopolysaccharides→ surfactant secretion
39
Q

What is the role of the surfactant secretion from the eustachian tube?

A

Keeps tube patent

40
Q

Properties of the epithelial lining associated with the auditory ossicles

A
  • Simple squamous to cuboidal epithelial lining
    • has pharyngeal mucosal origin
    • contains secretory goblet cells
41
Q

What structures are found around the tympanic bulla?

A

Various nerves run in or close to the wall of the bulla
Facial nerve
Branches of facial nerve and vagus nerse
Post ganglionic fibres of cervical sympathetic trunk

42
Q

Outline the topographical course of the facial nerve?

A
  • Enters petrous temporal bone through internal acoustic meatus
  • runs inside the facial canal

Intermediate components enters the tympanic cavity near oval window

43
Q

What fibres branch off the intermediate facial nerve

A
  • Greater petrosal nerve
  • stapedial nerve (motor)
  • chorda tympani nerve to the tympanic membrane
44
Q

Where does the facial nerve emerge?

A

Stylomastoid foramen

45
Q

What are the main structures of the inner ear?

A
  • vestibule
  • Cochlea
  • semicircular canals

all encased in a bony labyrinth of petrous temporal bone

46
Q

What are the functions of the inner ear?

A
  • Hearing
  • balance
  • position and rotation of head in relation to gravitational forces
47
Q

What is the normal microflora of the external ear?

A

Initially showed staphylococcal colonisation of skin and ears

Then recognised malassezia pachydermatis yeast organisms

  • non lipid dependent
  • Brad based budding organisms
48
Q

Outline the process of taking a cytology sample on the external ear

A
  • samples taken with cotton bud
  • rolled onto slide
  • may be heat fixed
  • stained with DiffQuik or Rapistain
  • Examined under X400-1000 magnification
49
Q

What techniques are used when assessing a patient for ear disease?

A
  • Physical examination of the external portions of the outer ear
  • General clinical examination (including relevant parts of the neurological exam)
  • Otoscopy- Using a hand held otoscope
  • Video otoscopy
  • Imaging
50
Q

Otitis?

A

Inflammation of the ear
otitis externa- auditory canal
Otitis media- mucosa of the nose eustachian tube, middle ear
Otitis interna- inner ear structure

51
Q

Otitis of which region of the ear is likely to impair cranial nerve 13?

A

Otitis interna
Hearing loss and peripheral vestibular disease

52
Q

Define perpetuating ear disease

A

factors that do not initiate inflammation but lead to exacerbation of the inflammatory process and maintain ear disease even if the primary factor has been identified and corrected

Bacteria such as staphylococcys and pseudomonas can be perpetuating factors

53
Q

What are the 3 main radiographic views of the ear?

A

Dorsoventral
Lateral oblique
Rostrocaudal (open mouth)

54
Q

What is the main cat ear mite?

A

Otodectes cynotis

Veterinary medicine year 2 (23 decks)

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