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Regional Gross Anatomy > Region 14 - Ear > Flashcards

Region 14 - Ear Flashcards

1
Q

What structures make up the external ear?

A

Auricle
External auditory meatus
External surface of tympanic membrane

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2
Q

What structures make up the middle ear?

A

Internal surface of tympanic membrane
Tympanic cavity
Ossicles
Pharyngotympanic tube

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3
Q

What structures make up the inner ear?

A 
Auditory apparatus
Vestibular apparatus
Internal acoustic meatus
CN VIII
Oval window
Round window
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4
Q

What is the auricle made up of?

A

Irregularly-shaped plate of elastic cartilage

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5
Q

Where does lymph from the auricle drain to?

A

Parotid and cervical nodes

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6
Q

What is the arterial supply to the auricle from?

A

Anterior auricular branches of superficial temporal artery

Posterior auricular artery perforating branches

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7
Q

What is the concha of the auricle? What is it made up of?

A

The deepest depression
Formed from:
- Cymba (superiorly)
- Cavity (inferiorly)

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8
Q

What is the sensory innervation to the auricle?

A

Anteriorly = Auriculotemporal nerve (CN V3)
Posteriorly = Lesser occipital nerve (C2) and Greater auricular nerve (C2-C3)
Entire auricle = Facial nerve contributions
Concha = Vagus nerve contributions

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9
Q

How long is the EAM?

A

~2.5cm

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10
Q

What type of cartilage makes up the lateral 1/3 of the EAM?

A

Elastic

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11
Q

What features are present in the lateral 1/3 of the EAM?

A

Hair follicles
Sweat glands:
- Ceruminous glands
Sebaceous glands

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12
Q

How does earwax form?

A

Mixing of secretions from sweat glands and sebaceous glands in lateral 1/3 of EAM

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13
Q

What is the structure of the medial 2/3 of the EAM?

A

Bone

Lined with stratified squamous epithelium

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14
Q

What is the arterial supply to the EAM?

A

Auricular branches of ECA

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15
Q

What is the sensory supply to the EAM?

A

External surface = Auriculotemporal nerve (CN V3)
Anterosuperiorly = Auriculotemporal nerve
Posteroinferiorly = Auricular branch of CN X
Posteriorly = Posterior auricular branch of CN VII

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16
Q

What is the diameter of the tympanic membrane?

A

~8mm

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17
Q

What is the outer surface of the tympanic membrane lined with?

A

Stratified squamous epithelium

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18
Q

What is the inner surface of the tympanic membrane line with?

A

Mucous membrane

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19
Q

What neurovascular structure crosses the inner surface of the tympanic membrane?

A

Chorda tympani of CN VII

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20
Q

What ossicle attaches to the inner surface of the tympanic membrane?

A

Malleus

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21
Q

What is the innervation to the lateral (external) surface of the tympanic membrane?

A 
Auriculotemporal nerve (anteriorly and superiorly)
Auricular branch of CN X (posteroinferiorly)
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22
Q

What is the innervation to the medial surface of the tympanic membrane?

A

Tympanic branches of CN IX

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23
Q

What forms the roof of the tympanic cavity (middle ear)?

A

Tegmen tympani:

  • Part of petrous temporal bone
  • Separates middle ear from dura of middle cranial fossa
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24
Q

What forms the floor/jugular wall of the tympanic cavity (middle ear)?

A

Layer of bone between:

  • Tympanic cavity AND
  • Superior bulb of IJV
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25
Q

What forms the membranous/lateral wall of the tympanic cavity (middle ear)?

A

Tympanic membrane
Superiorly:
- Lateral bony wall of epitympanic recess
- Head of malleus extends into recess

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26
Q

What forms the labyrinthine/medial wall of the tympanic cavity (middle ear)?

A

Promontory of labyrinthine wall:

  • Basal turn of cochlea
  • Oval and round windows
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27
Q

What overlies the promontory of the labyrinthine wall of the tympanic cavity?

A

Tympanic plexus:
- Lesser petrosal nerve
- Tympanic nerve
(Both CN IX)

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28
Q

What forms the mastoid/posterior wall of the tympanic cavity (middle ear)?

A

Aditus:

  • Opening in superior aspect of cavity
  • Opens into mastoid antrum
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29
Q

What forms the carotid/anterior wall of the tympanic cavity (middle ear)?

A

A thin bone between the tympanic cavity and the carotid canal

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30
Q

What features are in the superior part of the anterior wall of the tympanic cavity?

A

Opening for pharyngotympanic tube

Canal for tensor tympani

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31
Q

What is the origin and insertion of tensor tympani?

A 
Origin = Wall of pharyngotympanic tube
Insertion = Handle of malleus
32
Q

What is the function of tensor tympani?

A

Tenses tympanic membrane by pulling handle of malleus medially

33
Q

What is the innervation to tensor tympani?

A

CN V3

34
Q

What is the origin and insertion of stapedius?

A 
Origin = Pyramidic eminence on posterior wall of tympanic cavity
Insertion = Neck of stapes
35
Q

What is the function of stapedius?

A

Pulls ‘footplate’ of stapes laterally

36
Q

What is the innervation to stapedius?

A

Nerve to stapedius from CN VII

37
Q

What is the combined action of tensor tympani and stapedius?

A

Reduces vibration passing to delicate inner ear at the oval window

38
Q

What nerve provides sensory supply to the tympanic cavity?

A

CN IX

39
Q

What is the arterial supply to the tympanic cavity?

A 
Tympanic branches of:
- Posterior auricular artery
- Ascending pharyngeal artery
- Maxillary artery
Caroticotympanic artery from ICA
40
Q

How does the chorda tympani leave the tympanic cavity?

A

Via the petrotympanic fissure

41
Q

What is the structure of the lateral part of the pharyngotympanic tube?

A

1.2cm long
Bony canal
Lined with mucous membrane

42
Q

What is the structure of the medial part of the pharyngotympanic tube?

A

2.5cm

Cartilaginous and membranous tube

43
Q

What causes the pharyngotympanic tube to open?

A

Swallowing or yawning:

  • Tensor veli palatini contracts
  • Lumen opens
44
Q

What is the purpose of opening the pharyngotympanic tube?

A

Equalises pressure on both side of tympanic membrane

45
Q

What is the sensory supply to the pharyngotympanic tube?

A

Nerves from tympanic plexus (CN IX)

46
Q

What is the main arterial supply to the middle ear?

A

Anterior tympanic (glaserion) artery from 1st part (mandibular) of maxillary artery

47
Q

What other arteries supply the middle ear?

A

Ascending pharyngeal (inf. tympanic artery)
Middle meningeal (superior tympanic artery)
Posterior auricular:
- Stylomastoid artery
- Posterior tympanic artery
Artery of pterygoid canal
Caroticotympanic branch of ICA

48
Q

What surrounds the bone labyrinth of the inner ear?

A

Otic capsule:

  • Very dense bone within petrous temporal bone
  • NOT a part of bony labyrinth
49
Q

What are the canals of the bony labyrinth filled with?

A

Perilymph (similar to ECF)

50
Q

What are the structures of the bony labyrinth?

A

Cochlea
Vestibule
Semicircular canals

51
Q

What is the membranous labyrinth?

A

A continuous system of ducts and sacs within bony labyrinth

52
Q

What is the membranous labyrinth suspended in?

A

Perilymph

53
Q

What is the membranous labyrinth filled with?

A

Endolymph (similar to potassium ion-rich ICF)

54
Q

What are the functions of perilymph and endolymph?

A

Conduct sound vibrations
Respond to mechanical forces:
- Movement
- Acceleration

55
Q

What are the three main canals within the cochlea?

A

Scala vestibuli
Scala tympani
Cochlear duct

56
Q

What canal within the cochlea communicates with the stapes and where?

A

Scala vestibuli

At the oval window

57
Q

What canal within the cochlear communicates with the tympanic cavity and where?

A

Scala tympani

At the round window

58
Q

What are the scala vestibuli and scala tympani filled with?

A

Perilymph

59
Q

What separates the scala vestibuli and scala tympani?

A

Reissner’s membrane

60
Q

What is the cochlear duct filled with?

A

Endolymph

61
Q

What organ of hearing is found within the cochlear duct?

A

Organ of Corti

62
Q

How many turns does the cochlear have?

A

2.5

63
Q

What does the spiral canal of the cochlea turn around?

A

A bony core = Modiolus

64
Q

Where do the scala vestibuli and scala tympani communicate?

A

Helicotrema

65
Q

Where do the semicircular canals lie in relation to the vestibule?

A

Posterolaterally

66
Q

What is the structure of a semicircular canal?

A

2/3 of a circle

Diameter of ~1.5mm

67
Q

What are the semicircular canals?

A

Anterior and posterior (lie at right angles)

Lateral (lies horizontally)

68
Q

What are the semicircular ducts continuous with?

A

Utricle

69
Q

What is the swelling at the end of each semicircular canal? What does this contain?

A

Ampulla
Contains:
- Crista ampullaris which contains equilibrium sensors

70
Q

What do the ampullae of the semicircular canals respond to?

A

Angular (rotational) movements of the head

71
Q

How long is the vestibule of the bony labyrinth?

A

~5mm

72
Q

What membranous sacs are within the vestibule of the bony labyrinth?

A

Utricle

Saccule

73
Q

What equilibrium sensors are contained within the utricle and saccule? What movements do they respond to?

A

Maculae
Respond to:
- Gravity
- Changes in head position

74
Q

What is the main arterial supply to the inner ear?

A

Internal auditory (labyrinthine) artery

75
Q

What is the origin of the main arterial supply to the inner ear?

A 
Anterior inferior cerebellar artery (85%)
Basilar artery (15%)
76
Q

What are the branches of the main arterial supply to the inner ear?

A

Common cochlear artery

Vestibular artery

Regional Gross Anatomy (14 decks)

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