Figure 2.1

Question 1

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

Answer 1

Inner Ear
- Auditory placode; auditory pit

Middle Ear
-Tubotympanic recess begins to develop

Question 2

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

Answer 2

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

Question 3

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

Answer 3

Outer Ear

- Primary auditory meatus begins

Question 4

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

Answer 4

Inner Ear
- Utricle and saccule present; semicircular canals begin

Outer Ear
-Six hillocks evident; cartilage begins to form

Question 5

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

Answer 5

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

Outer Ear
- Auricles move dorsolaterally

Question 6

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

Answer 6

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

Question 7

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

Answer 7

Middle Ear

- Three tissue layers at tympanic membrane are present

Question 8

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

Answer 8

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

Question 9

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

Answer 9

Inner Ear

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

Question 10

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

Answer 10

Middle Ear

- Cartilaginous stapes formed

Question 11

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

Answer 11

Inner Ear
- Otic capsule begins to ossify

Middle Ear
- Ossification of malleus and incus beings

Question 12

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

Answer 12

Middle Ear

- Stapes begins to ossify

Question 13

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

Answer 13

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

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

Question 14

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

Answer 14

Middle Ear

- Meatal plug disintegrates, exposing tympanic membrane

Question 15

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

Answer 15

Middle Ear
- Pneumatization of tympanum

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

Question 16

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

Answer 16

Middle Ear

- Malleus and incus complete ossification

Question 17

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

Answer 17

Middle Ear

- Mastoid air cells develop

Question 18

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

Answer 18

Middle Ear

- Antrum is pneumatized

Question 19

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

Answer 19

Middle Ear

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