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HESP 645- Pediatrics > Lecture 1- Embryology > Flashcards

Lecture 1- Embryology Flashcards

1
Q

When does the trilaminar embryo develop?

A

Forms in 1st 3 weeks of development

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2
Q

What are the 3 components of the trilaminar embryo?

A

Ectoderm: neural tissue and surface epithelium

Mesoderm: most connective tissues of the body, muscle, bone, and cartilage

Endoderm: lining epithelium of the gastrointestinal, urogenital, and respiratory tract

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3
Q

What arises from the different trilaminar layers?

A

Otic placodes originate from thickenings of ectoderm

Middle ear originates from endodermal tissue

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4
Q

When do the pharyngeal arches develop?

A

By 4th week, 5 branchial grooves appear in lower head and neck region on the lateral surfaces

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5
Q

How many pharyngeal arches are there?

A

5

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6
Q

Which arches contribute to auditory development? Which part of the ear do they contribute to?

A

Pharyngeal arches 1 and 2 are main contributors to the middle/outer ear

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7
Q

What is the 1st branchial arch responsible for?

A

Responsible for most of the body structure of the malleus and incus

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8
Q

What is the 2nd branchial arch responsible for?

A
  • Lenticular process of the incus
  • Handle of the malleus
  • Stapes
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9
Q

When does the auricle begin to develop? What does it arise from?

A

Develops during 3rd or 4th week from the 1st and 2nd branchial arches

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10
Q

What development occurs during the 3rd week of fetal development?

A

Inner Ear
- Auditory placode; auditory pit

Middle Ear
-Tubotympanic recess begins to develop

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11
Q

What development occurs during the 4th week of fetal development?

A

Inner Ear
- Auditory vesicle (otocyst): vestibular-cochlear division

Middle Ear
-5 branchial grooves appear in lower head and neck region on lateral surfaces

Outer Ear
-Tissue thickenings begin to form

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12
Q

What development occurs during the 5th week of fetal development?

A

Outer Ear

- Primary auditory meatus begins

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13
Q

What development occurs during the 6th week of fetal development?

A

Inner Ear
- Utricle and saccule present; semicircular canals begin

Outer Ear
-Six hillocks evident; cartilage begins to form

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14
Q

What development occurs during the 7th week of fetal development?

A

Inner Ear
- One cochlear coil present; sensory cells in utricle and saccule

Outer Ear
- Auricles move dorsolaterally

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15
Q

What development occurs during the 8th week of fetal development?

A

Inner Ear

  • Ductus reuniens present; sensory cells in semicircular canals
  • Sensory end organs first appear as localized thickenings of epithelium in the utricle and saccule

Middle Ear
- Incus and malleus present in cartilage; lower half of tympanic cavity formed

Outer Ear
- Outer cartilaginous one-third of external canal formed

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16
Q

What development occurs during the 9th week of fetal development?

A

Middle Ear

- Three tissue layers at tympanic membrane are present

17
Q

What development occurs during the 11th week of fetal development?

A

Inner Ear

  • 2.5 cochlear coils present
  • Nerve VIII attaches to cochlear duct via ductus reuniens
  • Cochlear division of the 8th nerve follows the elongating and coiling of the cochlear duct
18
Q

What development occurs during the 12th week of fetal development?

A

Inner Ear

  • Sensory cells in cochlea
  • Membranous labyrinth complete
  • Otic capsule begins to ossify
19
Q

What development occurs during the 15th week of fetal development?

A

Middle Ear

- Cartilaginous stapes formed

20
Q

What development occurs during the 16th week of fetal development?

A

Inner Ear
- Otic capsule begins to ossify

Middle Ear
- Ossification of malleus and incus beings

21
Q

What development occurs during the 18th week of fetal development?

A

Middle Ear

- Stapes begins to ossify

22
Q

What development occurs during the 20th week of fetal development?

A

Inner Ear
- Maturation of inner ear; inner ear adult size

Outer Ear
- Auricle is adult shape but continues to grow until age 9

23
Q

What development occurs during the 21st week of fetal development?

A

Middle Ear

- Meatal plug disintegrates, exposing tympanic membrane

24
Q

What development occurs during the 30th week of fetal development?

A

Middle Ear
- Pneumatization of tympanum

Outer Ear
- External auditory canal continues to mature until age 7

25
Q

What development occurs during the 32nd week of fetal development?

A

Middle Ear

- Malleus and incus complete ossification

26
Q

What development occurs during the 34th week of fetal development?

A

Middle Ear

- Mastoid air cells develop

27
Q

What development occurs during the 35th week of fetal development?

A

Middle Ear

- Antrum is pneumatized

28
Q

What development occurs during the 37th week of fetal development?

A

Middle Ear

  • Epitympanum is pneumatized
  • Stapes continues to develop until adulthood -
  • Tympanic membrane changes relative position during first 2 years of life
29
Q

What are genetic abnormalities?

A

Thought to be within 1st 2 weeks of development as the zygote

  • Chromosomal
  • Translocation of chromosomal segments
  • Single gene mutation
30
Q

What are some external ear abnormalities that can be indicative of middle ear bone abnormalities?

A

Thickened lobes: abnormal incus and stapes

Smaller cup ears w/ absent cartilage: mennonite genetic absences of incus and stapes

Absent superior crus: congenital ossicle fixation

31
Q

What is anotia?

A

Occurs when pharyngeal arch hillocks fail to form
- Impacts EAM and ME bones

Known genetic causes: Treacher Collins Syndrome, hemifacial microsomia, congenital aural atresia

32
Q

What are some characteristics of Treacher Collins Syndrome?

A
  • Downward-slanting eyes
  • Small jaw and chin
  • Alters development of facial bones and tissues
33
Q

What is microtia?

A

Smaller cup ear or overfolded auricle

Can be associated with:

  • Hearing and vision abnormalities
  • Neurological abnormalities
  • Clefting of the face and palate
  • Musculoskeletal abnormalities
34
Q

How does Fetal Alcohol Syndrome (FAS) affect the external ear?

A

Lower or uneven external ear position
“Railroad track” ear
- Auricle has a curve at the top part of the ear, which is underdeveloped and folded over parallel to the curve beneath

35
Q

What is FAS associated with?

A

Delayed auditory function

SNHL

Intermittent CHL due to recurrent serous otitis media

36
Q

What is absence of the ossicles associated with?

A

Dwarfism and achondrogenesis

Incus/stapes are most common bones to be absent

37
Q

Inner ear cochlear and semicircular canal abnormalities are due to what genetic effects?

A
  • The Trisomies
  • Michel aplasia (absence of inner ear labyrinth)
  • Pendred Syndrome (abnormalities of the cochlea, enlarged vestibular aqueduct, thyroid enlargement)

HESP 645- Pediatrics (11 decks)

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