Ear Anatomy and Physiology Flashcards

1
Q

What are the 3 areas of the ear?

A
  • External
  • Middle
  • Inner
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2
Q

What is the pinna?

A
  • Stratified keratinised epithelium (skin)
  • Elastic cartilage
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3
Q

What is the external ear canal made of?

A

Lateral 1/3rd made of skin and cartilage:

  • Skin containing ceruminous and sebaceous glands (producing wax)
  • Thick hairs on the outside, become finer on the inside
    • Protective barrier and disinfectant

Medial 1/3rd made of skin and bone

  • No hairs or cilia
  • Doesn’t produce wax
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4
Q

How do the lateral and medial 1/3 of external ear canal differ?

A

Lateral 1/3rd made of skin and cartilage:

  • Skin containing ceruminous and sebaceous glands (producing wax)
  • Thick hairs on the outside, become finer on the inside
    • Protective barrier and disinfectant

Medial 1/3rd made of skin and bone

  • No hairs or cilia
  • Doesn’t produce wax
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5
Q

How does skin grow in the external ear canal?

A

Skin is constantly being shed and renewed:

  • Grows from the umbo of the tympanic membrane outwards
  • Is shed in the lateral 1/3rd of canal and trapped in wax as part of cleaning mechanism
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6
Q

What can wax or other mechanical obstruction of the external ear canal cause?

A

Wax or other mechanical obstruction cause minimal hearing loss when compared with other problems in other parts of the ear

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7
Q

What are some examples of clinical problems of the ear canal?

A
  • Earwax
  • Pinna haematoma
  • Cauliflour ear
  • Otitis externa
  • Fungal infection
  • Foreign body
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8
Q

What are the 3 layers of the tympanic membrane?

A
  • Outer layer is continuous with skin of external ear canal
  • Middle fibrous layer
  • Inner layer of respiratory epithelium (ciliated columnar epithelium with goblet cells)
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9
Q

How long is the external earn canal in adults?

A

4cm

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10
Q

How large is the diameter of the tympanic membrane?

A

1cm in diameter

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11
Q

What does the tympanic membrane seperate?

A

Separate the middle ear from the external ear

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12
Q

Where are ossicles found?

A

Middle ear

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13
Q

What is the function of ossicles?

A
  • Conduct sound waves from tympanic membrane to inner ear
  • Play an important role in sound conduction
    • Much more important than tympanic membrane
    • Disruption can be from trauma or bony sclerosis (otosclerosis)
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14
Q

What kind of epithelium is the middle ear lined with?

A

Lined with same continuous respiratory epithelium that forms inner layer of tympanic membrane:

  • keratinized stratified squamous epithelium
  • Capable of producing mucus
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15
Q

What nerve is found in the middle ear?

A

Middle ear contains the facial nerve

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16
Q

What are some important anatomical relations of the middle ear?

A
  • Middle cranial fossa
  • Internal carotid artery
  • Sigmoid sinus and internal jugular vein
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17
Q

What are the 6 segments of the facial nerve?

A
  • Intracranial
  • Meatal (internal auditory meatus)
  • Labyrinthine
  • Tympanic (fallopian tube)
  • Mastoid
  • Extratemporal
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18
Q

What does the facial nerve innervate?

A

The facial nerve is the motor supply to the muscles of facial expression:

  • Stapedius
  • Posterior belly of digastric
  • Stylohyoid
19
Q

Where does taste come from?

A

Taste comes from the anterior 2/3rds of tongue from the chorda tympani

20
Q

What nerve is used for taste?

A

Chorda tympani, which is a branch of the facial nerve

21
Q

What are examples of middle ear clinical problems?

A
  • Otitis media
  • Tympanic membrane perforation
  • Otitis media with effusion (OME)
  • Grommets
  • Cholesteatoma
22
Q

What are some possible complications of ottitis media and cholesteatoma?

A
  • Remember anatomical relations
    • Meninges
    • Middle cranial fossa
    • Facial nerve
    • Mastoid cavity
    • Inner ear
    • Sigmoid sinus/internal jugular vein
23
Q

Cholesteatoma - pathology

A
  • Misnomer, nothing to do with cholesterol
  • To do with skin of the middle ear
    • Keratinised squamous epithelium in the wrong place
  • Cause problems because they grow and are destructive
24
Q

What nerves innervate the ear?

A
  • Jacobsons nerve
    • Tympanic branch of glossopharyngeal nerve (CN IX)
    • Sensation to middle ear
  • Arnolds nerve
    • Auricular branch of vagus nerve (CN X)
    • Sensation to posterior half of external ear canal
  • Facial nerve (CN VII)
    • Anterior half of external ear canal
  • Mandibular branch of trigeminal nerve (CN V3)
    • Pinna (upper half)
  • Greater auricular nerve (C2/3)
    • Pinna (lower half)
25
Q

What parts of the ear do the following nerves innervate:

  • Jacobsons nerve
  • Arnolds nerve
  • Facial nerve
  • Mandibular branch of trigeminal nerve
  • Greater auricular nerve
A
  • Jacobsons nerve
    • Tympanic branch of glossopharyngeal nerve (CN IX)
    • Sensation to middle ear
  • Arnolds nerve
    • Auricular branch of vagus nerve (CN X)
    • Sensation to posterior half of external ear canal
  • Facial nerve (CN VII)
    • Anterior half of external ear canal
  • Mandibular branch of trigeminal nerve (CN V3)
    • Pinna (upper half)
  • Greater auricular nerve (C2/3)
    • Pinna (lower half)
26
Q

What is the Jacobsons nerve a branch of?

A
  • Jacobsons nerve
    • Tympanic branch of glossopharyngeal nerve (CN IX)
    • Sensation to middle ear
27
Q

What is the Arnolds nerve a branch of?

A
  • Arnolds nerve
    • Auricular branch of vagus nerve (CN X)
    • Sensation to posterior half of external ear canal
28
Q

Where do the following receive nerve innervation from:

  • middle ear
  • external ear canal
  • pinna
A
  • Jacobsons nerve
    • Tympanic branch of glossopharyngeal nerve (CN IX)
    • Sensation to middle ear
  • Arnolds nerve
    • Auricular branch of vagus nerve (CN X)
    • Sensation to posterior half of external ear canal
  • Facial nerve (CN VII)
    • Anterior half of external ear canal
  • Mandibular branch of trigeminal nerve (CN V3)
    • Pinna (upper half)
  • Greater auricular nerve (C2/3)
    • Pinna (lower half)
29
Q

What is otalgia?

A

Otalgia = ear pain

30
Q

What are examples of secondary causes of otalgia?

A
  • C2/3
    • Arthritis/cervical spondylosis
    • Soft tissue injury
  • CN V
    • Dental
    • TMJ dysfunction
    • Nasopharyngeal disease
  • CN IX
    • Oropharyngeal inflammation/infection
    • Tongue base malignancy
  • CN X
    • Laryngeal/pharyngeal malignancy
31
Q

What is the inner ear?

A

Bony and membranous labyrinth:

  • Membranous labyrinth contains fluid, perilymph and endolymph
32
Q

What does the menbranous labyrinth contain?

A
  • Membranous labyrinth contains fluid, perilymph and endolymph
33
Q

In what part of the ear is the membraneous labyrinth in?

A

Inner ear

34
Q

In what part of the ear are chochlear found?

A

Inner ear

35
Q

In what part of the ear are peripheral vestibular apparatus found?

A

Inner ear

36
Q

What are cochlear?

A
  • Organ of corti, hearing organ
37
Q

What makes up the peripheral vestibular apparatus?

A
  • Utricle
  • Saccule
  • Semicircular canals
38
Q

What nerve supplies the inner ear?

A

Vestibulocochlear nerve (CN VIII)

39
Q

Describe the process of hearing?

A
  • Function of middle ear to the transduce vibration into nervous impulses
  • Foot of stapes vibration in oval window
  • Causes pressure wave through fluid in cochlear
  • This is detected by hair cells in organ of corti
  • Transmitted to brainstem (junction of pons and medulla) by CN VIII
40
Q

Where is ‘hearing’ transfered to by CNVIII?

A

Transmitted to brainstem (junction of pons and medulla) by CN VIII

41
Q

What is responsible for the detection of:

  • head rotation
  • linear acceleration in vertical plane
  • linear acceleration in horizontal plane
A
  • Head rotation
    • Semicircular canals
  • Linear acceleration in vertical plane
    • Saccule
  • Linear acceleration in horizontal plane
    • Utricle
42
Q

What allows you to fix your vision on an object even when your head is moving?

A
  • Vestibulo-ocular reflex is what makes you able to fix your vision on an object even when your head is moving
43
Q

What parts of the ear are used for balance?

A
  • Peripheral vestibular apparatus
    • Semicircular canals
    • Saccule
    • Utricle
44
Q

What are the main organs of the:

  • external ear
  • middle ear
  • inner ear
A

External ear:

  • Pinna and external ear canal

Middle ear:

  • Tympanic membrane and ossicles

Inner ear:

  • Organ of corti for hearing
  • Semicircular canals/utricle/saccule for part of balance