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Head and Neck Anatomy > Anatomy of the Ear > Flashcards

Anatomy of the Ear Flashcards

1
Q

The ear is divided into what 3 parts?

A
  1. External
  2. Middle
  3. Inner
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2
Q

What are the functions of the ear?

A
  1. Hearing
  2. Balancing - equilibrium
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3
Q

What are the parts of the external ear?

A
  1. Auricle - collects sound
  2. External acoustic meatus (passage or canal) - conducts sound to the tympanic membrane
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4
Q

What is the pinna (auricle)?

A

Elastic cartilage covered by skin

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5
Q

Name the depressions of the pinna/auricle?

A
  • concha
  • helix
  • antihelix
  • tragus
  • antitragus
  • lobule : devoid of cartilage (fibrous tissue, fat and blood vessels)
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6
Q

What is the function of the outer ear?

A
  1. Collect sound
  2. Localization
  3. Resonator
  4. Protection
  5. Sensitive (earlobe)
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7
Q

What is the arterial supply of the auricle?

A
  1. Posterior auricular
  2. Superficial temporal arteries
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8
Q

What is the nerve supply of the auricle?

A
  1. Great auricular - lateral surface
  2. Aurculotemporal nerves (branch of CN V3) - skin superior to external acoustic meatus
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9
Q

What is the lymphatic drainage of the auricle?

A
  1. Superficial parotid lymph nodes
  2. Mastoid lymph nodes (retroauricular)
  3. Superficial cervical lymph nodes
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10
Q

Describe the structure of the external acoustic (auditory) meatus?

A
  1. outer third is cartilaginous and is covered by skin
  2. inner two thirds is bony covered by thin skin continuous with external layer of the tympanic membrane
    - has somewhat tortuous downward and forward course: pull auricle upward and backward to straighten
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11
Q

Describe the production of ear wax?

A

cerumin and sebaceous glands in outer half of external acoustic meatus produce cerumen (ear wax)

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12
Q

What is the nerve supply of the external acoustic (auditory) meatus?

A

Cutaneous sensation
1. Trigeminal - auriculotemporal
2. vagus - auricular branch

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13
Q

What is the tympanic membrane?

A

Separates the external ear and the middle ear (tympanic cavity)

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14
Q

Describe the appearance of the tympanic membrane through an otoscope?

A
  • Concavity towards the external acoustic meatus
  • Has a shallow cone-like depression at the center - the umbo,
  • “cone of light,” radiates anteroinferiorly from the umbo
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15
Q

What are the subdivisions of the tympanic membrane?

A
  1. Pars flaccida
  2. Pars tensa
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16
Q

Describe the surfaces of the tympanic membrane?

A
  1. Lateral surface - concave
  2. Medial surface - convex
    Note: most convex region = Umbo
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17
Q

What is between the fibrous and mucous layer of the tympanic membrane?

A
  1. Handle of malleus
  2. Crossed medially - chorda tympanic nerve
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18
Q

Describe the histological structure of the tympanic membrane?

A
  1. Outer cuticular layer
    - keratinised, hairless & devoid of dermal papillae
  2. Intermediate fibrous layer
    - outer radiating & inner circular fibres
  3. Inner mucous layer
    - simple columnar or squamous
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19
Q

Describe the nerve supply of the tympanic membrane?

A
  1. Auriculotemporal nerve (CN V3)
    - It is a branch of mandibular division of trigeminal nerve and supplies anterior half of lateral surface of TM
  2. CN X (vagus nerve)
    - Its auricular branch (Arnold’s nerve) supplies to posterior half of lateral surface of TM.
  3. CN IX (glossopharyngeal nerve)
    - Its tympanic branch (Jacobson’s nerve) supplies to medial surface of tympanic membrane.
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20
Q

Where does the external auditory canal end?

A

External auditory canal ends at tympanic membrane which vibrates against malleus on other side

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21
Q

What is inside the middle ear chamber?

A

malleus -› incus -› stapes
- which vibrates on oval window of inner ear

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22
Q

Name the muscles that inhibit vibration when sound is too loud?

A
  1. Tensor tympani m. (inserts on malleus)
  2. Stapedius m. (inserts on stapes)
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23
Q

Where is the middle ear?

A

Lies in the petrous temporal bone

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24
Q

The middle ear consists of what 2 regions?

A
  1. Tympanic cavity and mucous membrane
  2. Epitympanic recess
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25
Q

The middle ear is connected to?

A
  1. Nasopharynx
    - by auditory (Eustachian) tube
  2. mastoid air cells
    - by mastoid antrum
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26
Q

Pneumatization from the nasopharynx?

A

Lined with mucosa like pharynx
- retrograde infection from pharynx
e.g. otitis media, mastoiditis.

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27
Q

What is the sensory innervation of the middle ear?

A

Glossopharyngeal nerve

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28
Q

The middle ear contains?

A
  1. Auditory ossicles
    - malleus, incus and stapes
    - joined by synovial joints
    Clinical note: ankylosis, otosclerosis
  2. Muscles
    - stapedius : Facial nerve (VII)
    - tensor tympani : Mandibular nerve (V3)
    - dampen sounds and protect inner ear
  3. Nerves
    - The chorda tympani nerve (a branch of facial nerve CN VII)
    - The tympanic plexus of nerves (branch of glossopharyngeal)
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29
Q

Name the walls of the middle ear?

A
  1. Roof (tegmental wall)
  2. Floor (jugular wall)
  3. Lateral (membranous)
  4. Medial wall (labyrinthine)
  5. Anterior wall (carotid)
  6. Posterior wall
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30
Q

What are the components of the roof (tegmental) wall?

A

Tegment tympani
- thin plate of bone that separates tympanic cavity from dura in floor of middle cranial fossa

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31
Q

What are the components of the floor (jugular wall) of the middle ear?

A

A layer of bone that separates cavity from superior bulb of internal jugular vein

32
Q

What are the components of the lateral wall?

A

Tympanic membrane with epitympanic recess superiorly

33
Q

What are the components of the medial wall?

A

Separates tympanic cavity from inner ear

34
Q

What are the components of the anterior wall?

A

Separates tympanic cavity from carotid canal
- superiorly lies opening of eustachian tube and canal of tensor tympani

35
Q

What are the components of the posterior wall?

A

Connected by aditus to mastoid antrum and air cells

36
Q

Describe the mastoid antrum?

A
  • Is a cavity in the mastoid process of the temporal bone
  • The aditus (opening) to the antrum connects the mastoid antrum to the epitympanic recess
  • The tegment tympani separates the antrum from the middle cranial fossa
  • The floor of the antrum communicates with the mastoid air cells via several openings
  • The antrum and the air cells are lined by mucosa
  • Antero-inferiorly, the antrum is related to the canal for the facial nerve
37
Q

What is the auditory tube?

A
  1. connects the tympanic cavity ot the nasopharynx
  2. The posterior third is bony while the rest is cartilaginous
  3. The mucosa is continuous with the tympanic cavity and the nasopharynx
  4. Nerve supply: tympanic plexus (tympanic branch IX)
38
Q

What is the function of the auditory tube?
How does it carry out this function?

A

Equalizes air pressure between the middle ear and the atmosphere
Note: Cartilaginous walls are apposed to each other
- Can be opened by contraction of levator veli palati and tensor veli palati (muscles of soft palate) through yawning, chewing etc

39
Q

What are the auditory ossicles?

A
  1. Malleus - is attached to the tympanic membrane
  2. Incus - connects malleus to stapes
  3. Stapes - is attached to the oval window
    - Auditory ossicles are covered by the mucous membrane lining the tympanic cavity
40
Q

What are the functions of the auditory ossicles?

A

Transmits vibrations from the tympanic membrane to the oval window
Note: there are two muscles associated with ossicles

41
Q

What are the middle ear muscles?

A
  1. The Stapedius
    - attaches to Stapes
    - Contracts in Response to Loud sounds
    - innervated by Facial (VI cranial)
    e.g. chewing, speaking
  2. The Tensor Tympani
    - Helps open Eustachian tube
42
Q

What are the muscles associated with the auditory ossicles?
Nerve supply?
Function?

A

Two muscles associated with ossicles
1. Tensor tympani
- medial pterygoid nerve branch of Mandibular V3
- dampens the vibrations of the tympanic membrane
2. Stapedius
- supplied by branch of facial nerve CN
VIl
- dampens the vibrations of the stapes

43
Q

What are the functions of the ligaments of the middle ear?

A
  1. restrict and confine the effect of ossicles to act as a lever
  2. restrict movements to reduce the chance of damage to the inner ear
  3. prevents distortion to sound
44
Q

What is the acoustic reflex?

A

The movement of the ossicles may be stiffened by two muscles, the stapedius and tensor tympani, which are under the control of the facial nerve and trigeminal nerve, respectively
- These muscles contract in response to loud sounds, thereby reducing the transmission of sound to the inner ear
> This is called the acoustic reflex

45
Q

What are the functions of the components of the inner ear?

A
  1. Cochlea - hearing
  2. Vestibule - static equilibrium
  3. Semicircular canals - dynamic equilibrium
46
Q

Where is the internal ear?

A

Lies in the Petrous temporal bone

47
Q

What special organ does the internal ear contain?

A

Vestibulocochlear organ

48
Q

What is the function of the internal ear?

A

Sound reception and balancing

49
Q

The internal ear consists of?

A
  1. Bony labyrinth
  2. Membranous labyrinth (sacs and
    ducts - contain endolymph)
    - The two structures are separated by space containing fluid called perilymph (resembles CSF)
50
Q

What is the bony labyrinth?

A

Fluid-filled space surrounded by otic capsule
- Its walls are made of dense bone that forms a otic capsule

51
Q

The cave of the bony labyrinth is composed of?

A
  1. Bony Cochlea
  2. Bony Vestibule
  3. Bony Semi-circular canals
52
Q

Describe the bony cochlea?

A
  1. Shell-shaped bony labyrinth that contains the cochlea duct - concerned with hearing.
  2. The spiral canal of the cochlea begins at the vestibule and winds around a bony core called modiolus
    - Modiolus contains: cochlea nerve + blood vessels
53
Q

The bony labyrinth communicates with?

A
  1. Subarachnoid space - through cochlear aqueduct
  2. Middle ear - through round
    window closed by secondary tympanic membrane
54
Q

Describe the bony vestibule?

A

Small oval chamber that contains components of balance system
• Contains:
1. Utricle
2. Saccule

55
Q

The bony vestibule is continuous with?

A
  1. Bony cochlea - anteriorly
  2. Bony Semi-circular canal - posteriorly
  3. Posterior cranial fossa - thr.
    Aqueduct of vestibule
56
Q

What is the aqueduct of vestibule?

A
  • Extends to the posterior surface of the petrous temporal bone to open in the internal acoustic meatus.
  • Contains the endolymphatic ducta and blood vessels.
57
Q

Describe the bony semi-circular canal?

A

Three canals:
1. Anterior
2. Posterior
3. Lateral
- These three lie perpendicular to each other
- They communicate with the bony vestibule posterosuperiorly
- At one end of each canal there is a swelling - the ampulla
- They contain semi-circular ducts

58
Q

What is the membranous labyrinth?

A

Consists of a series of ducts and sacs that communicate with each other in the bony labyrinth
- Contains the endolymph

59
Q

2 divisions of the membranous labyrinth?

A
  1. The membranous cochlear labyrinth
  2. Membranous Vestibular labyrinth
60
Q

3 components of the membranous vestibule labyrinth?

A
  1. Utricle and Saccule
  2. 3 semi circular ducts (superior, horizontal and posterior)
  3. The endolymphatic duct
61
Q

What are the utricle and saccule?

A

Otolith organs
- two sacs communicate through utriculosaccular duct from which
Endolymphatic duct arises
- Saccule communicates with cochlea through ductus reuniens
- Contain receptors ( in the macula) which respond to linear acceleration and the static pull of gravity

62
Q

What are the 3 semicircular ducts of the membranous labyrinth?

A
  • Opens in the utricle through 5 openings
  • contain hair cell receptors in the ampulary crest that respond to rotational acceleration in three different planes
  • They stimulate the sensory neurons whose cell bodies are in the vestibular ganglion
63
Q

What is the endolymphatic duct?

A
  • Traverses the vestibular aqueduct and emerges in the posterior cranial fossa.
  • Opens in the endolymphatic sac located under the dura mater
  • Reservoir for excess endolymph formed by blood capillaries.
64
Q

What is equilibrium?

A

Equilibrium is another function of the inner ear controlled by the vestibular apparatus
- the saccule and utricle of the vestibule and the 3 semicircular canals

65
Q

What are the 2 types of equilibrium?

A
  1. Static equilibrium refers to a state of balance relative to the force of gravity
  2. Dynamic equilibrium involves the maintenance
    of balance during sudden movements
66
Q

Static equilibrium is controlled by?

A

Static equilibrium is controlled by the sensory hairs within the macula of the utricle and saccule

67
Q

What are otoliths?

A

Ear rocks

68
Q

Dunction of the otolith membrane?

A

An otolithic membrane, studded with dense calcium carbonate crystals (otoliths), responds to gravity when head position is changed
- This movement opens transduction channels in the hair cells,
producing local potentials which summate to form nerve AP

69
Q

Dynamic equilibrium is controlled by?

A

Semicircular canals
In ampulla is the crista ampullaris - contains hair cells and supporting cells covered by a gelatinous mass called the cupula.
Neurological connections between eyes and semicircular canals - for tracking
- nystagmus

70
Q

What is nystagmus?

A

Involuntary rapid eye movements

71
Q

The membranous cochlear labyrinth is composed of?

A

composed of three spiraling chambers:
1. The cochlear duct scala media) - contains endolymph
2. Scala vestibuli (above cochlear duct - begins at oval window)
3. Scala tympani - end at round window
- Scala vestibuli and scala typmani contain perilymph and meet at helicotrema

72
Q

Cochlear duct?

A

The Cochlear duct (of corti):
Spiral blind tube suspended between :
1. the spiral ligament on the external wall of cochlear canal and
2. Osseous spiral lamina of modiolus

73
Q

Divisions created by the cochlear duct?

A

The duct divides the canal into two channels that communicate at helicotrema
1. Scala vestibuli (above cochlear duct - begins at oval window)
2. Scala tympani - end at round window

74
Q

Boundaries if the cochlear duct?

A

Roof -formed by vestibular membrane
Floor - formed by basilar membrane + outer edge of osseus spiral lamina

75
Q

What is the organ of corti?

A

The spiral organ of corti - receptor of auditory stimuli
- Covered by gelatinous tectorial membrane
Contains hair cells - tips of which are embeded in tectorial membrane

Head and Neck Anatomy (37 decks)

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