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Head and Neck Anatomy > The Ear 1 > Flashcards

The Ear 1 Flashcards

1
Q

What does the external ear consist of?

A
  • auricle/ pinna
  • external acoustic/ auditory meatus
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2
Q

What kind of framework does most of the auricle have?

A

Most of the auricle has a supporting elastic cartilaginous framework with skin firmly attached to this.

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3
Q

What is the surface of the auricle like?

A

It is thrown into numerous folds and depressions which collect sound waves and allow us to discrimate their direction more easily.

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4
Q

What is the outermost rim of the auricle called?

A

This is called the helix

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5
Q

What does the helix of the auricle run into?

A

It runs into the lobule.

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6
Q

Describe the lobule of the auricle.

A

The lobule is fleshy and has no fibrocartilganinous support.

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7
Q

What is the inner rim of the auricle called?

A

The inner rim is called the antihelix.

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8
Q

What does the antihelix of the auricle encircle?

A

It encircles a depper concave portion of the auricle called the concha.

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9
Q

What are hearing aid moulds carefully constructed to fit?

A

They are carefully constructed to fit the concha and the external auditory meatus with an air tight seal here.

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10
Q

Anteriorly, what projects laterally at the entrance of the external auditory meatus?

A

The tragus projects laterally a little as a spur of elastic fibrocartilage.

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11
Q

What can we use an auriscope to examine?

A

We can use an auriscope to examine the external auditory meatus and the membrane of its inner end which is called the tympanic membrane.

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12
Q

Why do we have to take great care when conducting an auriscope examination with a newborn child?

A

Because their external auditory meatus is very short.

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13
Q

In adults, what is the outer third of the external auditory meatus like?

A

The outer third is cartilaginous.

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14
Q

In adults, what is the inner section of the external auditory meatus like?

A

It is walled by bone.

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15
Q

What is the most of the bone that makes up the inner section of the external auditory meatus made up of?

A

It is formed by the tympanic plate of the temporal bone.

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16
Q

What is the shape of the external auditory meatus?

A

It is an S shaped curve which first curves anteriorly and then posteriorly and then anteroinferiorly to reach the tympanic membrane.

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17
Q

Is the tympanic membrane at a right angle to the external auditory meatus?

A

No, it is placed obliquely so that the anterior wall and the floor if the meatus are longer than the roof of the posterior wall

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18
Q

How can we straighten the meatus for auriscope examination?

A

We must pull the auricle upwards and backwards.

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19
Q

What is the characteristic features of the normal tympanic membrane?

A
  • certain parts of the malleus shine through the membrane
  • long handle of the malleus is attached to the inner surface of the membrane, seen as a streak passing down and back to a point just below its centre.
  • at the upper end of the long handle of the malleus, a small lateral process creates a prominence in the membrane
  • anterior and posterior folds extend upwards from the upper end of the handle to the periphery of the membrane.
  • between the anterior and posterior folds there is a flaccid part of the membrane
    • flaccid part of the membrane is vascular
  • tympanic membrane is drawn inwards at the handle so that the outer surface of the handle of the malleus is concave.

MLSFFC

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20
Q

What does light reflected from the auroscope produce in the anteroinferior quadrant of the tympanic membrane?

A

It produced a cone of light.

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21
Q

Where do the external auditory meatus and external aspect of the tympanic membrane recieve sensory nerve fibres from?

A
  • vagus nerve = 10th cranial nerve
  • trigeminal nerve = 5th cranial nerve
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22
Q

What is the middle ear also called?

A

The tympanic cavity.

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23
Q

Describe the tympanic cavity?

A

This is a small air filled space within the petrous temporal bone.

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24
Q

How does the tympanic cavity communicate with the pharynx?

A

It communicates with the pharynx in front through the auditory tube which is sometimes called the eustachian tube or pharyngotympanic tube.

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25
Q

What does the tympanic cavity communicate with behind?

A

It communicates with the mastoid antrum.

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26
Q

Describe the upper part of the tympanic cavity?

A

The upper part is expanded into an epitympanic recess.

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27
Q

What does the middle air contain that connects the tympanic membrane to the membrane of the inner ear?

A

It contains 3 small bones or ossicles that connect these 2 membranes.

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28
Q

What do the ossicles of middle ear do?

A

They transmit vibrations across the cavity from the external ear to the internal ear.

Therefore we have mechanical coupling between the vibrations of the tympanic membrane and the vibrations of fluid within the inner ear.

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29
Q

What different walls does the tympanic cavity have?

A

It has a lateral, medial, anterior and posterior wall as well as a roof and floor.

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30
Q

What is the size of the tympanic cavity?

A

About the size of a hearing aid battery with similar proportions.

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31
Q

What is the lateral wall of the tympanic cavity formed of?

A

It is formed of the tympanic membrane.

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32
Q

What is the medial wall of the tympanic cavity made of?

A

It is made of the bone of the inner ear.

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33
Q

What are the some of the grooves and eminences that are produced by structures within the bone of the inner ear that make up the medial wall of the tympanic cavity?

A
  • promontory – rounded elevation on the medial wall that is produced by the cochlea
  • behind the promontory there are 2 openings that lead to bony cavities
    • upper opening = fenestrae vestibuli (oval window)
      • closed by the stapes which is one of the middle ear ossicles
    • lower opening = fenestrae cochleae (round window)
      • closed by the secondary tympanic membrane
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34
Q

What does the the anterior wall of the tympanic cavity lead it?

A

It leads to 2 canals which are the auditory tube and the canal for the tensor tympani muscle.

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35
Q

Out of the auditory tube and the canal for the tensor tympanic muscle, which is the lower and larger of the 2?

A

The auditory tube.

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36
Q

How does the auditory tube reach the pharynx?

A

It passes obliquely towards the pharynx.

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37
Q

How does the auditory tube change?

A

First it is within the petrous part of the temporal bone but it continues through the pharynx as a cartilaginous tube.

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38
Q

What is the function of the auditory tube?

A

It acts as a protective mechanis for the middle ear by allowing pressure to be equalised on the 2 sides of the tympanic membrane at all times.

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39
Q

When does the auditory tube open?

A

This tube opens during swallowing and yawning.

The cartilaginous part is related to several muscles that are active during swallowing and yawning.

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40
Q

What is the nerve supply to the mucous membrane of the auditory tube?

A

It is supplied by the glossopharyngeal nerve which is the 9th cranial nerve.

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41
Q

What do we have above the auditory tube?

A

We have the canal for the tensor tympani muscle.

42
Q

Describe the path of the tensor tympani muscle.

A
  • enters the tympanic cavity
  • gives rise to a delicate tendon which changes direction to reach its insertion into the handle of the malleus by passing around a small bony pulley called the processus trochleariformis.
43
Q

How is the canal conducting the interal carotid artery through the skull related to the anterior wall of the middle ear?

A

With only a thin lamina separating the two.

44
Q

What is the opening in the posterior wall of the tympanic cavity called?

A

This is called the aditus

45
Q

What does the aditus lead from, into?

A

It leads from the epitympanic recess to the mastoid antrum.

46
Q

What do we find on the posterior wall of the tympanic cavity, below the aditus?

A

We find a small pyramidal eminence that is containing the stapedius muscle.

47
Q

What does the pyramid of the stapedius muscle pass out of?

A

It emerges through the summit of the pyramid and travels from the summit to its insertion.

48
Q

Where is the insertion of the stapedius muscle?

A

The insertion is into the stapes.

49
Q

Describe the roof of the tympanic cavity.

A

The roof is thin and formed by parts of the petrous temporal bone called the tegmen tympani.

50
Q

What do we have above the roof of the tympanic cavity?

A

We have the temporal lobe of the brain.

51
Q

What is the floor of the tympanic cavity related to?

A

It is related to the jugular foramena and the internal jugular vein.

52
Q

What are the 3 ossicles called and where are they found?

A

The three ossicles are called:

  1. malleus
  2. incus
  3. stapes

They are found in the tympanic cavity.

53
Q

How are the 3 ossicles united?

A

They are united by synovial joints.

54
Q

What does the malleus look like?

A

Like a hammer.

55
Q

Where does the head of the malleus lie?

A

The head of the malleus lies in the epitympanic recess.

56
Q

How is the head of the malleus held in place in the epitympanic recess?

A

It is held in place there by ligaments.

57
Q

What is the handle of the malleus attached to?

A

The handle of the malleus is firmly attached to the inner surface of the tympanic membrane.

58
Q

How does the head of the incus articulate with the malleus?

A

It articulates with the malleus at a saddle shaped synovial joint.

59
Q

How is the incus anchored to the wall of the epitympanic recess?

A

The incus has a short process that is anchored to the wall of the epitympanic recess.

60
Q

What does the long process of the incus articulate with?

A

It articulates with the head of the stapes at a tiny synovial ball and socket joint.

61
Q

Describe the path of the long handle of the incus.

A

The long process of the incus runs downwards and backwards in the middle ear cavity in parallel with the long handle of the malleus.

62
Q

What does the footplate of the stapes fit into?

A

It fits into and closes off the oval window or fenestrae vestibuli of the inner ear.

63
Q

Where does the stapedius muscle attach to?

A

It attached to the neck of the stapes.

64
Q

What is the mastoid antrum?

A

This is an air sinus within the petrous part of the temporal bone and it lies behind the middle ear.

This is the only air sinus that is well developed at birth even though the mastoid process of the temporal bone is not formed at this time.

65
Q

Why is the mastoid antrum important clinically?

A

It is important because of the possibility of spread of infection into the mastoid antrum from the middle ear.

66
Q

What does the aditus in the anterior wall of the mastoid antrum lead to?

A

It leads to the epitympanic recess.

67
Q

What is the mastoid antrum related to posteriorly?

A

Posteriorly it is related to sigmoid sinus and here the bone may be quite thin.

68
Q

What is the roof of the mastoid antrum related to?

A

It is related to the brain.

69
Q

What is the medial wall of the mastoid antrum related to?

A

It is related to the posterior semicircular canals.

70
Q

When does the mastoid process start to develop?

A

The mastoid antrum does not begin to develop until the second year of life.

71
Q

Describe how the mastoid process develops in the second year of life?

A

Air cells gradually extend into the mastoid process and the cavities inside are continuous with the mastoid antrum and the tympanic cavity.

72
Q

Other than the mastoid process, where else can air cells be found?

A

Air cells can also be found in other parts of the petrous temporal bone.

A group of air cells extends as far as the apex of the petrous temporal bone.

73
Q

What is the mucous membrane of the mastoid air cells supplied by?

A

They are supplied partly by the mandibular division of the trigeminal nerve via the nervous spinosus which passes up to the mucous membranes via the foramen spinosum.

Glossopharyngeal fibres (9th cranial nerve) from the middle ear also contribute.

74
Q

What does the deeper part of the petrous temporal bone contain?

A

It contains a series of cavities and canals called the bony labyrinth.

75
Q

What are the bony cavities in the bony labyrinth filled with?

A

They are filled with a fluid called perilymph.

76
Q

Where are the organs of hearing and balance?

A

They are inside the complex network of the bony labyrinth as the membranous labyrinth.

77
Q

What do the organs of hearing and balance contain?

A

They contain endolymph.

78
Q

Is the membranous labyrinth afloat in the bony labyrinth?

A

No, it is anchored to the bony labyrinth at several points.

79
Q

What is the centrally placed cavity of the bony labyrinth called?

A

This is called the vestibule.

80
Q

What does the vestibule communicate with behind?

A

It communicates with 3 bony semicircular canals behind

81
Q

What does the vestibule lead to in front?

A

In front it leads to a curled bony nala called the cochlea.

82
Q

What does the bony labyrinth contain?

A

It contains perilymph.

83
Q

What does the composition of perilymph resemble?

A

It resembles the composition of CSF.

84
Q

What is the pathway of the aqueduct of the cochlea?

A

It passes through the petrous temporal bone from the cochlea to the jugular foramen and into the subarachnoid space?

85
Q

What is said to flow along the aqueduct of the cochlea?

A

There is a flow of CSF along this duct.

86
Q

Where is it likely that perilymph originates from?

A

It is likely that it originates as a transudate from blood vessels in the walls of the bony labyrinth.

87
Q

How can perilymph be removed?

A

It can be removed through the aqueduct of the cochlea but there are other mechanisms as well.

88
Q

What is the fenestrae vestibuli?

A

This is an opening on the lateral wall of the vestibule.

89
Q

What is the fenestrae vestibuli closed in life by?

A

It is closed by the footplate of the stapes in life.

90
Q

What will happen if there is movement of the stapes?

A

If there is movement of the stapes then this will transmit pressure waves to the perilymph of the vestibule.

91
Q

What is the cochlea?

A

This is a sinuous tunnel that runs forwards from the cavity of the vestibule.

92
Q

What does the shape of the cochlea resemble?

A

It resembles the shell of a snail with approximately 2 and 3/4 turns

93
Q

What is the apex of the cochlea called?

A

It is called the cupula.

94
Q

What does the cupula lie deep to?

A

It lies deep to the medial wall of the tympanic cavity.

95
Q

How is the promontory formed on the medial wall of the middle ear cavity?

A

The first turn of the cochlea raises a bulge called the promontory on the medial wall of the middle ear cavity.

96
Q

What is the modiolus?

A

The cochlea is wound around a central axis called a modiolus.

97
Q

How is the canal of the cochlea divided?

A

It is divided by a bony spiral lamina which projects from the central column into the canal.

98
Q

Aside from the bony spiral lamina, what else divides the canal of the cochlea?

A

The division of the canal of the cochlea is completed by a basilar membrane which stretches from the edge of the spiral lamina to the outer wall of the canal.

99
Q

How is the canal of the cochlea divided?

A

It is divided into a scala vestibuli above and a scala tympani below.

100
Q

How are the scala vestibuli and scala tympani continuous?

A

They are continuous through a gap at the apex of the cochlea called the helicotrema.

101
Q
A

Head and Neck Anatomy (36 decks)

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