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Funk Anatomy - NS Exam 3 > Ear Anatomy and Embryology > Flashcards

Ear Anatomy and Embryology Flashcards

1
Q

What is the function of the auricle?

A

Collect and funnel soundwaves towards the EAM

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2
Q

What are the cartilages which make up the auricle?

A

Helix, antihelix, and tragus

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3
Q

What are the external features of the auricle?

A

Concha and scaphoid fossa

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4
Q

What is the blood supply to the auricle (2)?

A

Superficial temporal and posterior auricular aa. and vv.

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5
Q

What is the sensory innervation of the auricle (5)?

A

Lesser occiptal (C2,3), great auricular (C2,3), auriculotemporal (V3), facial (VII), and vagus (X) nn.

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6
Q

What is epithelium which lines the EAM and what is the external acoustic canal composed of?

A

Lined by stratified squamous epithelium. Lateral 1/3 is cartilaginous and medial 2/3 is bony.

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7
Q

What is the blood supply of the EAM (3)?

A

Superficial temporal a.v., posterior auricular a.v., and deep auricular a.

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8
Q

What is the innervation of the EAM (2)?

A

Auriculotemporal (V3) and vagus (X) nn.

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9
Q

What is the lymphatic drainage of the EAM?

A

deep cervical nodes

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10
Q

What is the function of the tympanic membrane (3)?

A

Convert sound waves into vibrations of the middle ear ossicles. Amplifies sound waves via the ossicles and protects against loud sounds via the stapedius and tensor tympani mm.

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11
Q

What does the auricle derive from embryologically?

A

The mesenchyme of the 1st and 2nd pharyngeal arches. Specficially, 6 auricular hillocks will form the definitive auricle.

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12
Q

Auricular defects are commonly associated with what syndromes?

A

Chromosomal

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13
Q

What embryonic structure forms the EAM?

A

The 1st pharyngeal cleft

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14
Q

What is the meatal plug and what happens if it fails to degenerate?

A

The meatul plug is a proliferation of epithelium which occludes the EAM. It degenerates around month 7. If it fails to degenerate it will lead to deafness.

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15
Q

What embryonic structure forms the tympanic membrane?

A

The external epithelium of the tympanic membrane develops from the endoderm of the 1st cleft. The middle CT of the tympanic membrane forms the mesoderm of the 1st arch. The internal epithelium forms from the endoderm of the 1st pouch.

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16
Q

What forms the roof of the tympanic cavity?

A

Tegmen tympani of the temporal bone separates the epitympanic recess and the middle cranial fossa.

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17
Q

What forms the floor of the tympanic cavity?

A

A thin portion of the temporal bone separating the tympanic cavity form the internal jugular vein.

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18
Q

What forms the lateral wall of the tympanic cavity?

A

Tympanic membrane

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19
Q

What forms the medial wall of the tympanic cavity? What 3 features are found here?

A

A bony wall separating the inner and middle ear. The oval window which contacts the stapes and opens to the vestibule of the inner ear. The promontory represents the mound of bone formed by the cochlea. The round window acts as a release valve for maintaining the pressure of the fluids of the inner ear, opens to scala tympani.

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20
Q

What forms the posterior wall of the tympanic cavity? What are 2 features found here?

A

temporal bone. The facial canal contains the facial n. The aditus ad antrum is an opening to the mastoid antrum.

21
Q

What is mastoiditis?

A

This is infection of the mastoid antrum which has spread from the middle ear. The middle ear can be infected via the auditory tube. It is possible to enter the middle cranial fossa from the mastoid antrum.

22
Q

What forms the anterior wall of the tympanic cavity?

A

Segment of temporal bone separating the tympanic cavity from the carotid canal.

23
Q

Where does the auditory tube enter the tympanic cavity and what does it do?

A

Enters the tympanic cavity in the anterior wall. Balances the pressure on the inside and outside of the tympanic membrane.

24
Q

What is the composition of the auditory tube?

A

lateral 1/3 = bone and medial 2/3 = cartilage

25
Q

What muscle opens the auditory tube?

A

Tensor veli palatini

26
Q

What are the ossicles and their interactions?

A

Malleus - contacts the tympanic membrane creating the umbo and transfers vibrations to the incus

Incus - transfers vibrations from the malleus to the stapes

Stapes - contacts the oval window and transfers vibrations of the ossicles to the fluid in the cochlear duct

27
Q

What are the features of the tympanic membrane (3)?

A

Umbo - central concavity of the tympanic membrane
Pars Flaccida - superior thin portion
Pars Tensa - inferior thick portion

28
Q

What is the external and internal blood supply of the tympanic membrane?

A

External - deep auricular a. from maxillary a.

Internal - anterior tympanic a. from maxillary a.

29
Q

What is the internal and external sensory innervation of the tympanic membrane?

A

External - auriculotemporal and vagus nn.

Internal - glossopharyngeal n.

30
Q

What is the action and innervation of the stapedius?

A

Dampens movement of the ossicles. Innervated by CN VII (SVE).

31
Q

What is the action and innervation of the tensor tympani?

A

Dampens movement of the ossicles. Innervated by CN V3.

32
Q

What embryonic structure forms the tympanic cavity and auditory tube?

A

The 1st pharyngeal pouch

33
Q

What embryonic structure forms the malleus, incus, and tensor tympani m.?

A

The 1st pharyngeal arch

34
Q

What embryonic structure forms the stapes and stapedius m.?

A

The 2nd pharyngeal arch

35
Q

What can congenital fixation of stapes result in?

A

Deafness

36
Q

What arteries supply blood to the middle ear (5)?

A

Inferior tympanic a. via acending pharyngeal a.
Superior tympanic a. via middle meningeal a.
Anterior tympanic a. via maxillary a.
Posterior tympanic a. via stylomastoid a.
Tubal a. via the A. of pterygoid canal

37
Q

What provides the venous drainage of the middle ear?

A

Pterygoid venous plexus

38
Q

Describe CN IX’s innervation of the middle ear.

A

The tympanic branch of IX enters the middle ear though the tympanic canaliculus. It will form a tympanic plexus on the promontory of the middle ear, which provides GVA and GVE-P innervation to the middle ear and auditory tube. The tympanic plexus will reform on the opposite side to create the lesser petrosal n. (GVE-P)

39
Q

Describe CN VII’s innervation of the middle ear.

A

The facial nerve enters the middle ear through the facial canal. Here the chorda tympani extis the facial canal and provides SVE innervation to the stapedius m. It continues between the malleus and incus to exit via the petrotympanic fissure. Provides SVA to tongue and GVE-P to the submandibular and sublingual glands.

40
Q

What is the cochlea?

A

Spiral shaped bony structure surrounding the cochlear duct.

41
Q

What is the modiolus?

A

Central core around which the cochlea spirals 2.5x

42
Q

What is the spiral ligament?

A

Ligament which anchors the cochlear duct to the wall of the cochlea

43
Q

What is the osseous spiral lamina?

A

anchors cochlear duct to the modolius

44
Q

What is the membranous labyrinth?

A

membranous ducts within the bony labyrinth which contain endolymph.

45
Q

What is the function of the endolymphatic duct?

A

Passes from the vestibule through the vestibular aqueduct to terminate as the endolymphatic sac. It serves to regulate the volume and composition of the endolymph.

46
Q

What are the components of the cochlear duct?

A

Vestibular membrane - forms the roof of the cochlear duct and separates it from the scala vestibuli
Basillar membrane - forms the floor of the cochlear duct and separates it from the scala tympani
Spiral Organ (of Corti) - hair cells and tectorial membrane

47
Q

Describe how sound is transduced into nerve impulses

A

Sound waves enter the EAM and cause vibration of the tympanic membrane. This vibration is transferred via the ossicles to the perilymph of the bony labyrinth. The movement of the perilymph causes motion of the basillary and vestibular membranes which will cause motion in the endolymph. This will cause the tectorial membrane to move across the hair cells.

48
Q

What embryonic structure forms the membranous labyrinth?

A

Otic placode –> otic pit –> otic vesicle

49
Q

What embryonic structure forms the bony labyrinth?

A

Forms from mesenchyme surrounding the membranous labyrinth.

Funk Anatomy - NS Exam 3 (13 decks)

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