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W21 - 9525 > Wk 1 - ME Anatomy & Development > Flashcards

Wk 1 - ME Anatomy & Development Flashcards

1
Q

What are the 3 stages of human prenatal development?

A

Pre-embryonic (0-3 wks)
Embryonic (4-8 wks)
Fetal (9wks - birth)

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2
Q

Pathogens or trauma during which stage of prenatal development is likely to cause spontaneous abortion or miscarriage?

A

Pre-embryonic

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3
Q

Many developmental auditory disorders begin d/t maldevelopment at which prenatal stage?

A

Embryonic

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4
Q

High levels of noise exposure can cause cochlear damage during which prenatal stage?

A

Fetal

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5
Q

What happens during the pre-embryonic stage?

A
  • Fertilization
  • Cleavage of the zygote as it passes down the uterine tube
  • Implantation into the uterine wall
  • Hypoblast formation
  • Bilaminar disc formation
  • Formation of the primitive streak, notocord, & neural tube
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6
Q

What happens during the embryonic stage?

A
  • Development of the branchial structures
  • Initial formation of the external ear, TM, ME cavity and Eustachian Tube
  • Initial development of the cochlea duct, otic pit, utricle, saccule, and vestibular and cochlear portions of the membraneous labyrinth
  • Initial development of the pinnae
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7
Q

What happens during the fetal stage?

A
  • rapid growth and differentiation of organ systems
  • less susceptibility to teratogens
  • development of sensory structures of the ear
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8
Q

Newborns have very thin, flaccid pinnae. What are the implications of this?

A

The spectral transfer function at each location in space is less pronounced (less resonant), and so is less useful in elevation perception
- babies are able to localize in the horizontal plane by about 5 months; vertical localization matures beyond 1 year of age

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9
Q

Which branchial arches do the pinnae develop from?

A

1st (mandibular) and 2nd (hyoid)

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10
Q

What types of anomalies can we expect from abnormalities of the 1st branchial arch? Give 2 syndromic examples

A

Mandibular and ME anomalies

  • Treacher Collins Syndrome - abnormal outer ear, mandible, and lower eyelid
  • Pierre Robin Sequence - deformed mandible, eyes, ears, and cleft palate
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11
Q

Describe stenosis and atresia. What type of hearing loss can atresia cause?

A

Stenosis = partial closure of the ear canal

Atresia = complete closure of the ear canal; may cause 50-60 dB HL conductive loss

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12
Q

What type of maldevelopment can cause 10 dB of hearing loss at 5 kHz?

A

Anotia/absent pinna

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13
Q

T/F: Maldevelopment of the pinna often occurs in isolation

A

False - it will often occur with abnormalities of the ear canal - such as stenosis or atresia - as well

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14
Q

Microtia is due to incomplete development of which branchial arches before which week of gestation?

A

The 1st and 2nd branchial arches before the 5th week gestation

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15
Q

What syndromes have bilateral microtia?

A

Treacher Collins
Fraser, Nager, and Goldenhar syndromes
(most are genetic disorders associated with hearing loss)

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16
Q

What is it called when the pinna comes to a sharp point with forward folding (d/t deficiency in the 4th hillock/maldevelopment b/w 6th and 8th week gestation)?

A

Satyr Ear

17
Q

Describe Stahl Ear?

A
  • abnormality in superior crus of antihelix
  • may have “third” crus
  • poorly formed helix; hard, less elastic cartilage
  • may be d/t abnormality in uniting of 4th and 5th hillocks
18
Q

What is the name of the small growth that can occur at the superior part of the helix? What is is d/t?

A

Darwinian Tubercle

  • d/t small growth in the position of the 5th hillock
  • autosomal dominant trait
19
Q

What is Lop Ear?

A
  • down folding of helix and scapha

- problem with the intrinsic musculature or abnormal growth of 3rd hillock

20
Q

What is the name of the outer ear deformity that causes a cleft b/w the helix and the lobe?

A

Question Mark Ear

  • defects b/w 5th and 6th hillocks
  • maldevelopment may occur b/w 6th and 8th week gestation
21
Q

Name 3 differences in the EAM of infants compared to adults

A

In infants:

  • the TM is nearly parallel to the canal wall
  • TM is oval, not round
  • TM is thicker
  • EAM is ~3-5 mm shorter
  • EAM wall is thin cartilage, soft and compliant
22
Q

What impact does the thinner, more compliant EAM of infants have on resonant frequency?

A

Infants have a higher resonant frequency (~3.8 kHz vs ~3 kHz)

23
Q

The pinna forms from which 2 branchial arches?

A

1st and 2nd

24
Q

The EAM forms from which branchial cleft?

A

1st

- plug that degenerates fetally

25
Q

The TM has an external layer that is continuous with EAM (___-derm), an inner layer continuous with the ME cavity (___- derm) and a middle, fibrous layer

A

Ectoderm

Endoderm

26
Q

Cartilaginous derivatives of the 1st and 2nd branchial arch contribute to the development of _________

A

ME ossicles

27
Q

What ossicular structures does the 1st branchial arch contribute to?

A

Head and neck of malleus

Body and short process of incus

28
Q

The 2nd branchial arch contributes to with ossicular structures?

A
  • manubrium of malleus
  • long process of incus
  • head, neck, and footplate of stapes (lateral surface)
29
Q

The medial surface of the stapes footplate comes from which structure?

A

The Otic Capsule

30
Q

Ossicular anomalies often do not occur in isolation. If there is a single abnormality, what would we expect it to be?

A
  • Disconnection b/w incus and stapes

- Long process of incus is absent or abnormal and superstructure of the stapes malformed

31
Q

Malformation of the ossicular chain rarely occurs as a solitary lesion. What is it usually associated with?

A

Other temporal bone anomalies (atresia of the EAM)

32
Q

Due to the smaller size of the middle ear, what changes in impedance can we expect in infants?

A

Increased impedance

33
Q

The Eustachian tube develops from which structure?

A

The 1st pharyngeal pouch

34
Q

What is the purpose of the Eustachian Tube (ET)?

A

Ventilation and clearance

35
Q

Why do we see a lot of ear infections in young children?

A

The ET is short, straight, horizontal and narrow. Infants also only have one muscle (the tensor paliti) to open it (vs 2 in adults - the tensor paliti and levator paliti), and it’s close to the adenoids and can be easily blocked

W21 - 9525 (3 decks)

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