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BIOL21402 > L17 & L18 - Middle ear and facial nerve > Flashcards

L17 & L18 - Middle ear and facial nerve Flashcards

1
Q

Tympanic cavity: what is it, where is it located, what are its anatomical relations, and what does it do?

A

Air-filled chamber in the petrous part of the temporal bone

Just at the end of the sigmoid groove

  • Tympanic cavity proper medial to the tympanic membrane
  • Epitympanic recess superomedial to the tympanic membrane

Transmits sound from the outer ear

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2
Q

Tympanic cavity: what is contained in it and what is it in communication with?

A
  • The auditory ossicles (malleus, incus and stapes)
  • Tensor tympani and stapedius muscles
  • Chorda tympani (branch of the facial nerve, CN VII)
  • Tympanic nerve plexus

The nasopharynx via the eustachian tube and the mastoid air cells via the aditus and mastoid antrum

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3
Q

Mastoid ear cells

A

Dead end - travels down the inferior part of the mastoid process and no further

Near the pinna

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4
Q

What are the walls of the tympanic cavity?

A

Roof - tegmental wall
Floor - jugular wall
Lateral wall - membraneous wall
Medial wall - labyrinthine wall
Anterior wall - carotid wall
Posterior wall - mastoid wall

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5
Q

Tegmen tympani

A

Has a name

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6
Q

Tegmental wall: what part of the tympanic cavity wall is it, what is it formed from and what does it do?

A

Formed from tegmen tympani, a thin plate of bone

Separates tympanic cavity from middle cranial fossa (and brain)

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7
Q

Jugular wall: what part of the tympanic cavity wall is it, what is it formed from and what does it do?

A

Formed from bone

Separates tympanic cavity from the superior bulb of the internal jugular vein

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8
Q

Membraneous wall: what part of the tympanic cavity wall is it, what is it formed from and what does it do?

A

Part of the lateral wall

Formed from the tympanic membrane and lateral bony wall of the epitympanic recess

Separates tympanic cavity from the external ear

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9
Q

17.9

A

fully look at and understand the image

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10
Q

Labyrinthine wall: what part of the tympanic cavity wall is it, what is it formed from and what does it do?

A

Part of the medial wall

Formed from the lateral wall of the vestibule (including the oval window) and initial turn (including the round window) of the cochlea

Separates tympanic cavity from the inner ear

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11
Q

Mastoid wall: what part of the tympanic cavity wall is it, what is it formed from and what does it do?

A

Aditus links tympanic cavity to the antrum which in turn communicates with the mastoid air cells

Facial nerve canal is between the antrum and the posterior wall of the tympanic cavity

  • Contains bony air holes which allows it to stay strong and light
  • Sternocleidomastoid (and other muscles) attached to it
  • Lines with mucous membrane that is continuous with the lining of the tympanic cavity
  • Tegmen tympani separates the antrum from the middle cranial fossa
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12
Q

Carotid wall: what part of the tympanic cavity wall is it, what is it formed from and what does it do?

A

Part of the anterior wall

Contains openings of the pharyngotympanic tube
and the canal for the tensor tympani

Separates tympanic cavity from the carotid canal (and internal carotid artery)

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13
Q

Pathology of the facial nerve

A

Forceps around baby’s head - the mastoid process not protecting facial nerve yet

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14
Q

17.15

A

stopped listening, rewatch

Separates tympanic cavity from the carotid canal (and internal carotid artery)

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15
Q

Ossicles within the middle ear: what are they, what do they do, and where are they derived from?

A

Incus, Malleus, stapes

  • Transmit sound from the tympanic membrane to the cochlear
  • Increase the force of sound waves (x10-20)
  • Maintain the frequency of the sound waves

Splanchnocranium:
Incus (maxillary cartilage)
Malleus (Meckel’s cartilage)
Stapes (Reichert’s cartilage)

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16
Q

Incus, malleus, stapes: what items are they often related to due to their shapes?

A

Incus - anvil
Malleus - hammer
stapes - stirrup

17
Q

Why do we increase sound wave force when it enters the ear?

A

Density

Moving through the air is several times easier than moving through the more dense liquid within the ear so an increase in sound wave force is required

18
Q

Incus: what is it, what does it do, and what do its specific parts do?

A

Body of incus (anvil) is in epitympanic recess and articulates with the malleus

Transmits vibrations from the malleus to the stapes

  • Long limb articulates with head of the stapes
  • Short limb is connected by a ligament to the posterior of the tympanic cavity
19
Q

Malleus: what is it, what does it do, and where do its specific parts articulate to?

A

Handle of malleus (hammer) is embedded in the tympanic membrane

transmit sound from the tympanic membrane (ear drum) to the inner ear

  • Neck lies against the flaccid part of the tympanic membrane
  • Head in epitympanic recess and is in contact with incus
20
Q

Stapes: what is it, what does it do, and where do its specific parts articulate to?

A

Stapes (stirrup) is the smallest ossicle (and the smallest bone in the body) which fits into the oval window of the medial wall

Transmits sound waves to the cochlear

  • Has a head, neck, two limbs and a base
21
Q

Reflex to loud noise: which muscles act and what do they do?

A

Protect inner ear hair cells, instinctively contract tensor tympani and stapedius muscles to reduce damage

  • Reduce vibrations when contracted by moving the stapes away from the oval window and reducing vibration transmission
  • Protect against loud noises

If this is dulled ears become damaged

22
Q

Tensor tympani: what is it, where is its origin, where does it insert, and what is it innervated by?

A

Muscle that can decrease sound transmission through the middle ear

Has origin on the cartilaginous part of the pharyngotympanic tube, greater wing of the sphenoid and temporal bone

Inserts onto handle of malleus and tenses tympanic membrane

Innervated by the mandibular nerve (V3)

23
Q

Stapedius: what is it, where is its origin, where does it insert, what is it innervated by, what can occur if it is damaged, and are there any key facts about it?

A

Muscle that directly acts on the stapes

Origin inside pyramidal eminence of posterior wall

Inserts onto neck of stapes and pulls it posteriorly and tilts its base in the oval window

Innervated by a branch of the facial nerve (VII)

Hyperacusis – distorted and echoing sounds due to stapedius paralysis

Smallest muscle in the body

24
Q

Pharyngotympanic tube: what is its other name, what does it do, what is its structure, how does it exit, and what other key details does it have?

A

Eustachian tube

Communicates with the nasopharynx and equalises pressure between middle and external ears

Postero-lateral third is bony, the remainder is cartilaginous

Exits through foramen lacerum

  • Lined with mucous membrane
  • Walls normally in contact
  • Can be opened by contracting tensor veli palatini and levator veli palatini I.e. by yawning or swallowing

rewatch lecy - attention snapped

25
Q

rewatch leccy

A

Yawning, swallowing, blowing nose while holding etc

26
Q

Facial nerve: which cranial nerve is it, where does it arise from, where does it exit the cranial cavity, where does it supply motor fibres to, where does it supply sensory fibres to. and does it supply any other fibres?

A

CN VII

Arises from the ventral part of the brainstem between pons and medulla

Internal acoustic meatus

Motor:
* Muscles of facial expression
* Lacrimal gland
* Submandibular gland
* Sublingual gland
* Accessory salivary glands

Sensory:
* Anterior 2/3 of the tongue (taste)

Note: Also conveys some general sensory fibres from skin posterior to pinna to spinal and pontine trigeminal nucleus

27
Q

Facial nerve nuclei

A

Has 3 nuclei (on each side)
* Main motor
* Sensory
* Parasympathetic
Main motor nucleus
* Within pons
* Somatic motor fibres supply
facial muscles
* Muscles of upper part of face
receive bilateral innervation
* Muscles of lower part of face
receive unilateral innervation

Parasympathetic
* Posterolateral to main motor
nuclei
* Lacrimal nucleus supplies
secretomotor fibres to
lacrimal glands
* Receive fibres from sensory
nuclei of trigeminal nerve
* For reflex lacrimation following
conjunctival or corneal irritation
* Recieves sensory fibres from
hypothalamus
* For emotional response
* Also superior salivatory nucleus

Sensory nucleus
* Superior part of solitary nucleus
* Receives information about
taste sensation from anterior 2/3 of tongue

rewatch

28
Q

Motor nucleus

A

Decussate on upper neurones, lower than palpebral fissure will synapse at the contralateral smtn

Rewatch leccy

29
Q

Facial nerve pathway

A

rewatch leccy

30
Q

Lacrimal gland nerev supply

A

Parasympathetic, sympathetic and sensory fibres reach
the lacrimal gland via the lacrimal nerve
This is a branch of the ophthalmic nerve

rewatch leccy

31
Q

Petrotympanic fissure

A

Chorda tympani enter/exits the skull through it

32
Q

Stylomastoid foramen

A

Main part of the facial nerve (to facial muscles) exits skull through the stylomastoid foramen

33
Q

Facial nerve branches

A
  • Temporal branch
  • Buccal branch (of the facial nerve)
  • Marginal mandibular branch
  • Zygomatic branches
  • Cervical branch
  • Posterior auricular branch

Buccal/mandibular NOT to be confused with buccal/mandibular divisions of the trigeminal nerve

34
Q

Muscles of facial expression

A

Occipitofrontalis - wrinkles forehead (surprise)
Orbicularis oculi - sphincter of eye (closing)
Orbicularis oris - mouth sphincter (cheek puff)
Corrugator supercilii - raises eyebrows
Zygomaticus - elevate corners of mouth (smiling)
Platysma - tenses skin of neck (shaving)

35
Q

Platysma

A

origin of all facial muscles?

36
Q

Order of facial nerve branching

A

The zombies buried my cat

Temporal, Zygomatic, Buccal, Mandibular, Cervical

BIOL21402 (12 decks)

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