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(LUSUMA) Head, Neck & Neuroanatomy > S7) Functional Anatomy and Disorders of the Ear > Flashcards

S7) Functional Anatomy and Disorders of the Ear Flashcards

1
Q

What is the ear?

A

The ear is the organ of hearing and balance (equilibrium)

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2
Q

Different pathologies can involve the three different areas of the ear.

Identify these

A
  • External ear
  • Middle ear
  • Inner ear
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3
Q

Identify 6 signs/symptoms of ear disease

A
  • Otalgia (ear pain)
  • Tinnitus (ear ringing)
  • Discharge
  • Vertigo
  • Hearing loss (conductive vs sensorineural)
  • Facial nerve palsy
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4
Q

Within which bone of the skull do we find the parts of the ear?

A

Temporal bone

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5
Q

Identify the four components of the temporal bone

A
  • Squamous part
  • Petromastoid part
  • Tympanic plate
  • Styloid process
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6
Q

What is referred pain?

A

Referred pain is pain felt in a part of the body other than its actual source

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7
Q

What is the significance of otalgia?

A
  • Otalgia can sometimes be referred pain
  • Due to the diverse sensory innervation of the ear, sources outside of the ear that share similar nerve innervation may present with otalgia e.g. laryngeal cancers
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8
Q

State the components and function of the external ear

A
  • Components: pinna, external auditory meatus, lateral surface of tympanic membrane
  • Function: collects, transmits and focuses sound waves onto the tympanic membrane
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9
Q

What does the pinna of the external ear consist of?

A

The pinna consist of cartilage, skin and fatty tissue

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10
Q

Label the following surface features of the external ear:

  • Helix
  • Antihelix
  • Concha
  • Tragus
  • External auditory meatus
  • Lobule
A
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11
Q

Identify 4 causes of pinna abnormalities

A
  • Congenital
  • Inflammatory
  • Infective
  • Traumatic
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12
Q

When do pinna haematomas occur?

A
  • Secondary to blunt injury to the pinna
  • Common in contact sports
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13
Q

How do pinna haematomas occur?

A
  • Accumulation of blood between cartilage and perichondrium
  • Deprives the cartilage of its blood supply
  • Causes pressure necrosis of tissue
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14
Q

How are pinna haematomas treated?

A
  • Prompt drainage
  • Measures to prevent re‐accumulation and re‐apposition of two layers
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15
Q

What happens to untreated/poorly treated pinna haematomas?

A

Untreated or poorly treated leads to fibrosis and new asymmetrical cartilage development → ‘cauliflower deformity’ of the ear

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16
Q

How long is the external acoustic meatus?

A

2.5 cm

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17
Q

Describe the structure of the external acoustic meatus (ear canal)

A
  • Consists of a a cartilaginous (outer 1/3) and bony part (inner 2/3)
  • Skin-lined cul-de-sac
  • Sigmoid shape
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18
Q

Describe the anatomical location of the external acoustic meatus

A
  • Free outer border provides an attachment for external ear cartilage
  • Medially, it fuses with the petrous part of the temporal bone
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19
Q

Identify 4 functions of the external acoustic meatus

A
  • Arrangement of hairs and production of wax (cartilaginous part)
  • Prevent objects entering deeper into ear canal
  • Aids in desquamation and skin migration out of canal
  • Skin lining secretes cerumen to protect meatal skin
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20
Q

What are the components of ear wax?

A
  • Discarded cells of meatal skin
  • Cerumen (modified sebum)
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21
Q

Describe the structure, location and function of the tympanic membrane

A
  • Structure: fibrous structure, translucent
  • Location: apex points medially
  • Function: allows visualisation of some structures within the ear (malleus)
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22
Q

Identify two common conditions involving external acoustic meatus

A
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23
Q

Identify two common conditions affecting the tympanic membrane

A
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24
Q

Where are the middle and inner ear found?

A

The petrous part of the temporal bone contains the middle and inner ear

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25
Q

Describe the anatomical relations of the petrous part of the temporal bone

A

Upper surface forms part of the floor of the middle and posterior cranial fossae:

  • Internal acoustic meatus pierces the part forming the posterior cranial fossa
  • ICA and carotid canal are found in its inferior surface (irregular)
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26
Q

What is the middle ear?

A

The middle ear (aka tympanic cavity) is an air-filled cavity between the tympanic membrane and the inner ear, containing three ossicles

27
Q

Identify the 3 ossicles in the middle ear

A
  • Malleus
  • Incus
  • Stapes
28
Q

The ossicles lie in the upper part of the tympanic cavity.

Describe the articulations of its synovial joints

A
  • The handle of the malleus is attached to the tympanic membrane but its body articulates with the body of the incus
  • The incus then articulates wit the stapes
  • The stapes then articulates with the bony labyrinth of the inner ear at the oval window
29
Q

Describe the structure and function of the 3 ossicles of the middle ear

A
  • Structure: connected via synovial joints
  • Function:

I. Relay vibrations from the tympanic membrane to the oval window of the cochlea (inner ear)

II. Transmit vibration from an air medium to a fluid‐medium

30
Q

Movement in the middle ear is tampered by two muscles tensor tympani and stapedius.

What is their role?

A

Tensor tympani and stapedius muscles contract if potentially excessive vibration due to loud noise (protective; acoustic reflex)

31
Q

Identify and describe any pathology involving the ossicles

A
  • In otosclerosis, ossicles can become fused at articulations, between the base plate of stapes and oval window
  • Sound vibrations cannot be transmitted, causing deafness
32
Q

What are the roles of the mucous membrane and pharyngotympanic tube in terms of pressure in the middle ear?

A
  • Mucous membrane continuously reabsorbs air in middle ear causing negative pressure
  • Eustachian tube equilibrates pressure of middle ear with atmospheric pressure, also allowing for ventilation and drainage of mucus from the middle ear
33
Q

Describe the physiological cause of ‘ear popping’

A
  • The pharyngotympanic tube is usually closed
  • It intermittently opens when pulled by the attached palate muscles when swallowing/yawning
34
Q

What is posterior to the middle ear and why is this clinically significant?

A
  • Posteriorly, the middle ear communicates with the mastoid air cells via the mastoid aditus and antrum
  • This connection provides a potential route for infection (mastoiditis)
35
Q

Where is the mastoid antrum found?

A

The cavity of the mastoid antrum (a prolongation of the middle ear cavity) extends into the mastoid process and communicates with air cells

36
Q

Describe the pathophysiology of Otitis media with effusion (glue ear)

A
  • Otitis media with effusion is a build up of fluid and negative pressure in middle ear
  • Caused by Eustachian tube dysfunction (not infection), can predispose to infection and decreases mobility of TM and ossicles (affecting hearing)
37
Q

How can otitis media with effusion be resolved?

A
  • Most resolve spontaneously in 2‐3 months, but some may persist
  • Require grommets (tympanostomy tube) to ventilate middle ear
38
Q

What is acute otitis media and what are its symptoms?

A
  • Acute otitis media is an acute middle ear infection which is more common in infants & children
  • Symptoms: otalgia, red/bulging TM, loss of normal landmarks, temperature (non-specific)
39
Q

The pharygotympanic tube is shorter and more horizontal in infants.

What are the implications of this for infants?

A
  • Easier passage for infection from the nasopharynx to the middle ear
  • Tube can block more easily, compromising ventilation and drainage of middle ear, increasing risk of middle ear infection
40
Q

Identify 4 types of complications resulting from acute otitis media

A
  • Tympanic membrane perforation
  • Facial nerve involvement
  • Mastoiditis
  • Intracranial complications: meningitis, sigmoid sinus thrombosis, brain abscess
41
Q

Identify the important anatomical relations of the ear

A
42
Q

In terms of the anatomical relations of the ear, explain how mastoiditis might occur

A
  • Middle ear cavity communicates via mastoid antrum with mastoid air cells
  • Provides a potential route for middle ear infections to spread into the mastoid bone (mastoid air cells)
43
Q

Describe the anatomical relationship of the facial nerve with the middle ear and the significance of this

A
  • Facial nerve and one of its branches, the chorda tympani, runs through middle ear cavity.
  • Hence, facial nerve may be involved in pathology involving the middle ear
44
Q

What is a cholesteatoma?

A

Cholesteatoma is a rare abnormal skin growth (sac or cyst of skin cells) growing into into middle ear, behind the tympanic membrane

45
Q

Identify 3 possible symptoms of cholesteatoma

A
  • Causes painless, often smelly otorrhea (ear discharge)
  • Might cause hearing loss
  • Might potentially cause more serious neurological complications
46
Q

Describe the growth and development of a cholesteatoma

A
  • Secondary to chronic ET dysfunction or chronic/recurring ear infections
  • Not malignant but slowly grows and expands, eroding into structures e.g. ossicles, mastoid bone, cochlea
47
Q

Describe the formation of the inner ear (labyrinth)

A
  • The inner ear consist of a series of canals hollowed out of the petrous bone (bony labyrinth) which surround a series of ducts (membranous labyrinth)
  • The ducts of the membranous labyrinth are shaped to form the utricle, saccule, semicircular ducts and cochlear duct
48
Q

Identify and describe the components of the inner ear

A

Fluid-filled tubes:

  • Cochlea (bony labyrinth surrounding cochlear duct)
  • Vestibular apparatus (bony labyrinth surrounding saccule & utricle and contents)
49
Q

Describe the fluid found in the inner ear

A
  • Perilymph is found between the membranous and bony labyrinth
  • Endolymph fills the ducts of the membranous labyrinth
50
Q

What is the function of the cochlea of the inner ear?

A

The cochlea, containing the spiral organ of Corti, converts vibration into an electrical signal (action potential) which is perceived as sound

51
Q

What is the function of the vestibular apparatus of the inner ear?

A

The vestibular apparatus is involved in maintaining our sense of position and balance

52
Q

In 4 steps, describe how the vestibular apparatus maintain our sense of position and balance

A

⇒ Stereocilia in utricle and saccule respond to rotational acceleration & the static pull of gravity

⇒ Stereocillia in semicircular ducts respond to rotational acceleration in three different planes

⇒ Movement of head & body moves inner ear fluid, causing sterecilia to bend

⇒ Bending generates an action potential which is relayed to vestibular part of CN XIII and is perceived as our sense of position and balance

53
Q

The cochlea is our organ of hearing. It is fluid filled tube.

Describe how it functions

A
  • Movements at the oval window set up movements of the fluid in the cochlea
  • Waves of fluid cause movement of special sensory cells (stereocilia) within the cochlear duct which generate action potentials in CN VIII
54
Q

In 5 steps, explain how we hear

A

⇒ Auricle and external auditory canal focuses and funnels sound waves towards TM which vibrates

⇒ Vibration of the ossicles sets up vibrations/movement in cochlear fluid

⇒ Sensed by stereocilia (nerve cells) in the cochlear duct

⇒ Movement of the stereocilia in organ of Corti trigger action potentials in cochlear part of CN VIII

⇒ Primary auditory cortex make senses of the input

55
Q

Identify 3 diseases of the inner ear

A
  • Meniere’s Disease
  • Benign Paroxysmal Positional Vertigo

‐ Labrynthitis

56
Q

Identify 4 symptoms of pathology of the inner ear

A
  • Vertigo
  • Hearing loss (sensorineural)
  • Tinnitus
  • Nystagmus (involuntary eye movement)
57
Q

How does one examine a patient presenting with hearing loss?

A
  • Inspection of external ear and surrounding areas
  • Otoscopy
  • Gross hearing assessment
  • Tuning forks (Weber’s and Rinne’s test)
  • Referral for more formal audiometry testing
58
Q

Conductive hearing loss arises from pathology involving the external or middle ear.

Provide 4 examples

A
  • Wax
  • Otitis media
  • Glue ear
  • Otosclerosis
59
Q

Sensorineural hearing loss arises from pathology involving the inner ear structures or CN VIII.

Provide 4 examples

A
  • Presbycusis (most common type in >55 year olds)
  • Meniere’s Disease
  • Acoustic neuroma
  • Ototoxic medications
60
Q

What is the purpose of Rinne’s and Weber’s testing?

A

Rinne’s and Weber’s testing helps differentiate between a conductive and sensorineural hearing loss

61
Q

What is an acoustic neuroma?

A

An acoustic neuroma (aka vestibular schwannoma) is a benign brain tumour of the Schwann cells developing on the vestibulocochlear nerve, impairing hearing and balance

62
Q

What is Meniere’s disease?

A

Meniere’s disease is a condition of the inner ear which causes vertigo (dizziness with spinning sensation), hearing loss and tinnitus (ear ringing)

63
Q

What is labyrinthitis?

A

Vestibular neuritis is an inner ear infection wherein the labyrinth becomes inflamed causing vertigo, hearing loss, nystagmus (involuntary eye movement), tinnitus and the feeling of pressure in the ear

64
Q

Identify the structures observed in this otoscopic view of a normal external ear and lateral surface of the tympanic membrane:

A

(LUSUMA) Head, Neck & Neuroanatomy (19 decks)

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